Pipe Sizing Calculator — Flow Rate to Pipe Diameter
Enter a target flow, pick the fluid and the pipe series, and this tool walks every standard size from smallest to largest — computing true inside diameter, velocity, and Darcy–Weisbach pressure drop for each — then hands you the smallest bore that stays inside the limits. Water, gas, compressed air, and fuel lines included.
By Flow Calculator · Last updated: November 13, 2026
Sizing Inputs
= 0.00076 m³/s · 0.757 L/s
Kell density & Vogel viscosity at 20 °C — the same correlations the homepage engine uses. Supply design usually caps near 2.4 m/s.
True inside diameters from Copper tube — Type L.
≈ 7.9 ft/s
Recommended Pipe
1"DN ≈ 25
True inside diameter: 1.025 in / 26.0 mm
Velocity
1.42 m/s
4.67 ft/s
Pressure drop
3.87 psi/100 ft
87.5 kPa/100 m
Preliminary sizing estimates for planning and education — final sizing must follow applicable codes (IPC/UPC/IFGC), manufacturer data, and a licensed engineer where required.
Every Candidate Size in the Series
Velocity and Darcy–Weisbach pressure drop computed for your flow, fluid, and material — the smallest passing size carries the green badge.
| Nominal size | ID (in / mm) | Velocity (m/s · ft/s) | ΔP (psi/100 ft · kPa/100 m) | Status |
|---|---|---|---|---|
| 1/4" | 0.315 / 8.0 | 15.06 · 49.40 | 1149.01 · 25991.2 | FAILHigh FrictionOver Velocity |
| 3/8" | 0.430 / 10.9 | 8.08 · 26.51 | 252.53 · 5712.4 | FAILHigh FrictionOver Velocity |
| 1/2" | 0.545 / 13.8 | 5.03 · 16.50 | 80.27 · 1815.8 | FAILHigh FrictionOver Velocity |
| 5/8" | 0.666 / 16.9 | 3.37 · 11.05 | 30.56 · 691.3 | FAILHigh FrictionOver Velocity |
| 3/4" | 0.785 / 19.9 | 2.42 · 7.95 | 13.88 · 313.9 | FAILHigh FrictionOver Velocity |
| 1"Recommended | 1.025 / 26.0 | 1.42 · 4.67 | 3.87 · 87.5 | PASS |
| 1 1/4" | 1.265 / 32.1 | 0.93 · 3.06 | 1.41 · 32.0 | PASS |
| 1 1/2" | 1.505 / 38.2 | 0.66 · 2.16 | 0.62 · 14.0 | PASS |
How Flow Rate Becomes Pipe Diameter
Sizing a pipe is the flow-rate equation read backwards. The forward direction — the one the site’s formula reference prints in full — starts with a bore and a velocity and multiplies them into a flow. The sizing direction starts with the flow you need and asks what bore can carry it at a velocity you are willing to live with.
Q = A · v → A = Q / v → d = √(4A / π)
The required area comes from your flow and your chosen velocity; the diameter follows from the area.
ΔP = f · (L / D) · ρv² / 2 · Re = ρvD / μ
Darcy–Weisbach friction loss with the Colebrook–White friction factor f, iterated from the Reynolds number and the material’s roughness.
The first equation alone would size every pipe in the world — but it would size them badly. Velocity is a policy choice, not a law of nature: the same 12 GPM can sprint through a 3/4 in line at 2.4 m/s or stroll through a 1 in line at 1.4 m/s. The second equation is the referee. It prices each choice in pressure, and pressure is what your pump, your compressor, or your gas meter actually pays.
That is also why this tool carries the friction math instead of stopping at the area. When your known quantity is a pressure difference rather than a flow — a gauge reading, a regulator setpoint, a critical-flow condition — that is the opposite corner of the problem, and the orifice flow calculator works that direction instead.
Every bore is a decision, not a defaultPhoto: Unsplash💡 Tip — pick the criterion that matches the failure you fear
Short runs with noisy fixtures or hammering valves? Size by velocity. Long runs, gas lines, or anything fed by a pump or compressor with a fixed discharge pressure? Size by pressure drop. The calculator lets you switch without re-entering a single number.
Velocity Criteria: the Number that Decides the Size
Every pipe-sizing method funnels down to one question: how fast is the fluid allowed to move? Too fast, and the line hammers, sings, and erodes itself at every elbow. Too slow, and solids settle, biofilm takes hold, and you paid for steel that idles. The bands below are the ones this calculator defaults to for each fluid — they are typical industry practice values (the rule-of-thumb families collected in references such as Crane Technical Paper No. 410), not code mandates, and your governing code always wins where the two disagree.
| Fluid / service | Recommended band (m/s) | Recommended band (ft/s) | Data basis |
|---|---|---|---|
| Water supply — pressurized mains & branches | 1.2 – 2.4 | 3.9 – 7.9 | Typical industry practice — water hammer, noise, and fitting erosion set the ceiling |
| Pump suction lines | 0.6 – 1.5 | 2.0 – 4.9 | Typical industry practice — NPSH margin and cavitation avoidance |
| Drainage & gravity lines | ≥ 0.6 – 3 | ≥ 2.0 – 9.8 | Typical industry practice — self-cleansing floor of 0.6 m/s, invert-erosion ceiling |
| Compressed air — mains & headers | 6 – 9 | 20 – 30 | Typical industry practice — the ΔP budget usually decides first |
| Compressed air — branches & drops | 3 – 6 | 10 – 20 | Typical industry practice |
| Natural gas — low pressure | sized by ΔP | — | Fuel-gas code tables govern (IFGC / UPC); velocity is only a secondary screen |
Drainage deserves its own note: in a gravity line the depth of flow self-selects, so the “velocity” is an outcome rather than an input. That case — slope, depth, and self-cleansing tractive force — belongs to the open channel flow calculator, which solves the free-surface problem this pressurized tool deliberately does not.
Material Trade-offs: PVC, Copper, Steel, PEX
The same target flow lands on different answers depending on what the pipe is made of — because wall thickness sets the true bore, roughness sets the friction, and material limits set the ceiling. The matrix below is an indicative comparison, not measured data: dots rate how well each material fits each service, the cost column is a $ / $$ / $$$ band per installed foot, and the watch-outs are the risks that actually bite in the field.
| Material | Home water supply | Irrigation | Compressed air | Chemical / fuel lines | Cost | Watch-outs |
|---|---|---|---|---|---|---|
| PVC (Sch 40 / 80) | ●●●○○ | ●●●●● | ●○○○○ | ●●○○○ | $ | UV degradation outdoors · 140 °F temperature ceiling · brittle failure — widely prohibited for compressed air · thermal expansion ~10× steel |
| Copper tube (Type L) | ●●●●● | ●●●○○ | ●●●●○ | ●●○○○ | $$$ | Material cost · pitting in aggressive hard water (scale-sensitive) · theft value · solder/press tooling |
| Steel pipe (Sch 40) | ●●○○○ | ●●○○○ | ●●●●● | ●●●●○ | $$ | Corrosion & scale (ε ≈ 30× copper) · heavy, threaded/welded labor · rust downstream |
| PEX tubing (CTS) | ●●●●○ | ●●●●○ | ○○○○○ | ○○○○○ | $ | 200 °F temperature ceiling · UV sensitive · not rated for compressed air · smaller bore per nominal size (CTS) |
●●●●● = best fit for the service · five dots = strongest fit.
PVC — Schedule 40 / 80
Pros
- Cheapest per foot and per fitting
- Smoothest common bore (ε = 0.0015 mm) — low friction per dollar
- No corrosion, no scale; ideal buried with proper bedding
Cons
- 140 °F ceiling rules out hot service (typical material limit)
- UV degrades exposed runs — paint or bury it
- Brittle failure mode; widely prohibited on compressed air
Copper tube — Type L
Pros
- Thin walls mean more area per nominal size than steel
- 50+ year service life; handles hot water to code limits
- Fire-resistant, recyclable, compact for tight framing
Cons
- $$$ material cost — the budget line item
- Pitting corrosion in aggressive hard water
- Solder / press tooling adds labor cost
Steel pipe — Schedule 40
Pros
- The workhorse for compressed air, fuel, and process lines
- High pressure and temperature tolerance; Sch 80 for severe service
- Mechanically rugged for exposed industrial runs
Cons
- Rusts and scales — roughness grows over the pipe's life
- Heavy; threading and welding are skilled labor
- Rust slugs travel downstream to valves and tools
PEX tubing — CTS
Pros
- Cheapest retrofit: long coils, few fittings, fast pulls
- Freeze-tolerant and quiet in walls
- No solder — expansion or crimp joints only
Cons
- 200 °F ceiling (typical material limit)
- UV sensitive — never store or run it in sunlight
- Not rated for compressed air; smaller bore per nominal size
Material choice is a system decisionPhoto: UnsplashA Decision Tree that Holds Up in the Field
- Budget-tight and buried → PVC Schedule 40, laid on proper bedding; it is the cheapest water main per foot and never corrodes.
- Heat exchange, exposed heating loops, or anything hot → copper Type L; it is the thin-wall option with the temperature headroom.
- Industrial high-pressure air, fuel, or process duty → steel Schedule 80; Schedule 40 under moderate pressure, Sch 80 where wall is the safety case.
- Residential soft-water branches and retrofits → PEX; the lowest-labor path through existing framing.
❌ Don’t — PVC on compressed air
Unreinforced PVC is brittle and stores elastic energy; an impact or a pressure surge can shatter it into shrapnel, which is why many jurisdictions explicitly prohibit it for compressed air. Use steel, copper, or air-rated aluminum and rated hose.
Water Pipe Sizing Chart (GPM)
The chart below is computed live from the schedule presets on this page (steel Schedule 40, ASME B36.10M true inside diameters — the same registry the calculator reads). Each column answers one question: how many GPM does this bore deliver at the velocity mark? 1.5 m/s is quiet branch territory, 2.5 m/s is the usual main-line ceiling, and 4.5 m/s is the practical ceiling for steep short runs and drained or gravity-fed segments. Find your GPM, read left to the smallest size that carries it under your chosen mark, then verify pressure drop for your actual run length in the calculator.
| Nominal size | ID (in) | ID (mm) | GPM @ 1.5 m/s | GPM @ 2.5 m/s | GPM @ 4.5 m/s (gravity / upper limit) |
|---|---|---|---|---|---|
| 1/2" | 0.622 | 15.8 | 4.7 | 7.8 | 14.0 |
| 3/4" | 0.824 | 20.9 | 8.2 | 13.6 | 24.5 |
| 1" | 1.049 | 26.6 | 13.3 | 22.1 | 39.8 |
| 1 1/4" | 1.380 | 35.1 | 22.9 | 38.2 | 68.8 |
| 1 1/2" | 1.610 | 40.9 | 31.2 | 52.0 | 93.7 |
| 2" | 2.067 | 52.5 | 51.5 | 85.8 | 154.4 |
| 2 1/2" | 2.469 | 62.7 | 73.4 | 122.4 | 220.3 |
| 3" | 3.068 | 77.9 | 113.4 | 189.0 | 340.2 |
| 4" | 4.026 | 102.3 | 195.3 | 325.4 | 585.8 |
These capacities follow purely from area × velocity — Q = A·v. They say nothing about how far the water travels; that is the pressure-drop column’s job. The pipe-size presets section of the homepage lists the same true diameters side by side for steel Sch 40/80 and copper, if you want to compare materials at a glance.
Compressed Air Pipe Sizing
Compressed air is where two criteria compete most visibly, so this table states its assumptions explicitly. Every figure below was computed on this page with the same Colebrook engine as the calculator, under these conditions: steel Schedule 40 pipe, 100 psig line pressure, 70 °F air, and a capacity defined as the smaller of (flow at 9 m/s velocity) and (flow at a 1 psi per 100 ft pressure-drop budget). At 100 psig the air is about 7.8× denser than free air, which is why a modest-looking SCFM number can run surprisingly slow — and why the small sizes hit the pressure wall before the velocity wall.
| Size (steel Sch 40) | SCFM capacity | Velocity @ capacity (m/s) | ΔP / 100 ft @ capacity | Binding limit |
|---|---|---|---|---|
| 1/2" | 17 | 5.16 | 1.00 psi | ΔP budget |
| 3/4" | 35 | 6.22 | 1.00 psi | ΔP budget |
| 1" | 67 | 7.28 | 1.00 psi | ΔP budget |
| 1 1/4" | 138 | 8.70 | 1.00 psi | ΔP budget |
| 1 1/2" | 195 | 9.00 | 0.88 psi | Velocity |
| 2" | 321 | 9.00 | 0.65 psi | Velocity |
| 2 1/2" | 458 | 9.00 | 0.52 psi | Velocity |
| 3" | 707 | 9.00 | 0.40 psi | Velocity |
Read the last column carefully: through 1 1/4 in the pressure budget binds, and from 1 1/2 in upward the velocity cap does. Sizing a shop main purely by “comfortable velocity” can therefore leave you with a header that drops more pressure than your regulator can spare — exactly the failure the 30 SCFM preset in the calculator demonstrates when it lands on 3/4 in steel.
💡 Tip — budget for the leaks, not the nameplate
A typical uncompressed shop loses 20–30% of compressor output to leaks, and every quick-connect adds a little more. Size the distribution main for the demand your tools will actually draw at peak — usually nameplate air plus 25% — or the ring main will starve the far end of the shop on the first busy morning.
Pressure is the currency air mains spendPhoto: UnsplashNatural Gas and Fuel Lines
Gas sizing inverts the habit of the water world: instead of a velocity band, the governing quantity is the appliance’s input rating converted to gas volume. The trade conversion is CFH ≈ BTU/h ÷ 1,000, based on a supply gas heating value of roughly 1,000 BTU per cubic foot — a convention consistent with the IFGC’s sizing method. The table gives the common appliance loads and the branch sizes seen in typical practice for short runs; it is a sanity screen, not a final basis.
| Appliance | Input (BTU/h) | Gas demand (CFH ≈ BTU/h ÷ 1,000) | Typical branch (typical practice) |
|---|---|---|---|
| Range / cooktop | 50,000 – 80,000 | 50 – 80 | 1/2" – 3/4" |
| Tankless water heater | 150,000 – 199,000 | 150 – 200 | 3/4" short runs; 1" typical |
| Furnace | 60,000 – 120,000 | 60 – 120 | 1/2" – 3/4" |
| Clothes dryer | 20,000 – 25,000 | 20 – 25 | 1/2" |
| Fireplace | 25,000 – 40,000 | 25 – 40 | 1/2" – 3/4" |
⚠️ Warning — the code tables outrank any calculator
IFGC and UPC gas tables size branches from load, total developed length, and specific gravity, and they account for fittings that a straight-pipe velocity check ignores. Low-pressure gas delivers almost nothing in reserve: an undersized branch shows up as an appliance that lights fine alone but starves when the furnace kicks in. Use this page’s gas option (ρ ≈ 0.73 kg/m³, approximate) as a screening check, and let the code table own the final number.
Liquid fuels — diesel day-tank runs, generator feed lines, gasoline transfer — behave closer to the water case: pick the fluid, keep velocity near 1.5 m/s or below, and let pressure drop arbitrate. The calculator’s diesel and gasoline presets carry those defaults already.
Hidden Costs: Why the Bigger Pipe Often Wins
The purchase order only sees one side of pipe economics. Going one size up costs a few dollars per foot, once. Running too small charges rent forever, because friction compounds against velocity and the pump pays it every hour. The mechanism is in the Darcy equation: ΔP grows with the square of velocity, softened only slightly by the friction factor falling as the flow smooths out.
Run the numbers on the worked example’s pipe — 100 ft of 1 in Type L copper in water. At 12 GPM (1.42 m/s) the line loses about 3.9 psi per 100 ft and the pumping power is a rounding error: ΔP × Q ≈ 20 watts. Double the flow in the same pipe (24 GPM, 2.84 m/s) and the drop climbs to about 13.4 psi per 100 ft — a factor of ≈ 3.5, computed with the same Colebrook formulas as the calculator (≈ 3.8 in commercial steel; up to 4 where roughness dominates). Pump power scales as ΔP × Q, and Q doubled too, so the meter reads roughly 7× before — about 140 watts, forever, plus the noise and the hammer.
The lesson generalizes: within any reasonable pressure budget, the extra dollar for the next nominal size is repaid by the pump schedule, and the larger bore also buys headroom for the expansion you have not planned yet.
When the flow grows ×10, costs grow superlinearly
Take the same 100 ft of 1 in Type L and push 120 GPM through it — ten times the flow, same pipe:
- Velocity1.42 → 14.2 m/s
- Pressure drop3.9 → ≈ 250 psi/100 ft (×64)
- Pump power (ΔP × Q)20 W → ≈ 13 kW (×645)
- Same flow in 2 1/2 in Type L≈ 3.7 psi/100 ft → ≈ 195 W
Holding the same pressure budget does not need a ×10 area — but it does need the next two nominal sizes. That nonlinearity is why system expansions that “fit the existing pipe” on paper still need a pump quote before anyone signs.
⚠️ Warning — the lock-in cost of the wrong material
Material choice compounds like a migration decision. Swapping a framework later is a rewrite; repiping later is demolition, permits, drywall, and downtime — many times the cost of choosing correctly at rough-in. Pick the material for the service (the matrix above), then size within it.
Sizing Mistakes and Red Lines
Trap 1 — Sizing from the nominal diameter
Nominal size is a label, not a dimension. Look up three different “1 inch” pipes in the preset registry this page runs on:
- Steel Schedule 40, 1 inID 1.049 in
- Copper Type L, 1 inID 1.025 in
- PEX (CTS), 1 inID 0.891 in
The PEX bore carries 28% less area than the steel one — so the same flow runs nearly 40% faster in it. Any chart keyed to nominal size instead of true inside diameter is wrong by that margin before the first fitting is counted.
Trap 2 — Treating peak flow as continuous flow
Fixtures never all run at once, and compressors and tankless heaters surge. Sizing to the instantaneous peak gold-plates the pipe; sizing to the daily average starves the far end at the worst moment. Real design uses a demand factor: the probability-weighted load from the code tables, plus a margin for the surge events that matter — the washing machine valve snapping shut on a full-bore line is the classic water-hammer generator, and its violence scales with the velocity you allowed.
🚫 Red line — erosion and water hammer in steel
When computed water velocity exceeds roughly 8–10 m/s in steel pipe (typical design limit), erosion–corrosion at fittings and water-hammer damage risk rise steeply: the line must be upsized at least one nominal size, or the excess pressure must be managed with regulating valves, soft-closing actuation, or staged starts — not left to the pipe to absorb.
❌ Don’t — trust a single-number “GPM to pipe size” chart blindly
A chart that says “20 GPM = 1 inch” without naming the material, the velocity criterion, the run length, and the fluid temperature is hiding every assumption that matters. Use charts for orientation; let the calculator — or your code’s own tables — make the call.
Worked Example: 12 GPM of Water into a Copper Line
Every figure below reproduces in the calculator — press the 12 GPM · water · Copper L preset and the candidate table returns exactly these numbers, because the page and the prose share one engine.
STEP 1
State the demand
12 GPM of cold water — a whole-house branch or a heavy fixture cluster. The engine converts it to 0.757 L/s (7.571 × 10⁻⁴ m³/s) using the shared unit registry.
STEP 2
Try 3/4 in Type L first
ASTM B88 gives the true bore: 0.785 in / 19.94 mm ID → 312 mm² of area. Velocity = Q/A = 2.42 m/s (7.95 ft/s) — just over the 2.4 m/s supply ceiling. Verdict: not recommended; and its friction (≈ 13.9 psi/100 ft) fails a typical 5 psi/100 ft budget too, so both criteria agree.
STEP 3
Step up to 1 in Type L
True ID 1.025 in / 26.03 mm → 532 mm². Velocity falls to 1.42 m/s (4.67 ft/s) — PASS with margin. Colebrook (drawn-copper roughness ε = 0.0015 mm, Re ≈ 36,900, f ≈ 0.0226) gives ΔP ≈ 3.87 psi/100 ft (87.5 kPa/100 m) — inside the budget, about 1.5 psi over a 40 ft run.
STEP 4
Read the recommendation
1 in Type L copper (DN ≈ 25), 1.42 m/s, 3.87 psi/100 ft. The pump pays ~20 W per 100 ft for this line at perfect efficiency — the quieter, cheaper regime by a wide margin.
One flow, checked two waysPhoto: UnsplashNotice what decided the answer: velocity, not pressure. The 3/4 in line failed the 2.4 m/s ceiling by a hair and the pressure budget by a mile — but on a short run with generous supply pressure, a designer could legally accept its friction. What no designer should accept is 7.95 ft/s slamming fixture valves in occupied walls. The two criteria guard different failures, which is why this pipe sizing calculator makes you choose one deliberately and still reports the other.
This page is the reverse-direction twin of the main flow rate calculator: the homepage engine starts from a known diameter and asks what flow it delivers, while this pipe sizing calculator starts from a target flow and works backwards to the bore that carries it safely. If you are assembling a toolkit, the calculators hub collects every flow tool on the site — the orifice and open-channel calculators included — and each pairs with worked guides that explain the physics behind every input.
Data Sources & References
Pipe dimensions — ASME B36.10M
NPS Schedule 40/80 outside diameters and wall thicknesses, and the PVC schedules that reuse them, follow the ASME B36.10M tables — asme.org. True inside diameters on this page are computed as OD − 2×wall from those tables.
Copper water tube — ASTM B88
Type K / L / M outside diameters and wall thicknesses per astm.org Standard B88. PEX follows CTS dimensions. The worked example’s 0.785 in and 1.025 in bores trace to this standard.
Velocity bands & friction — industry practice
The velocity criteria and the erosion red line follow the rule-of-thumb families collected in Crane Technical Paper No. 410 (Flow of Fluids) and general piping design practice. They are typical values, labelled as such — not code limits.
Plumbing & fuel-gas codes — ICC
Water supply and drainage criteria trace to the IPC and UPC; gas branch sizing and the appliance-load method trace to the IFGC — codes.iccsafe.org. Where a code table and this tool disagree, the code table governs.
Fluid properties — shared engine
Densities and viscosities come from the same preset registry and correlations (Kell density, Vogel viscosity, ideal-gas law) that power every calculator on Flow Calculator, so a number here agrees with the same number there.
Pipe Sizing FAQ
How do I calculate pipe size from flow rate?▼
Four steps. Pick a design velocity for your fluid (2.4 m/s is a common cold-water ceiling). Divide flow by velocity to get the required cross-section: A = Q/v. Convert that area to a diameter: d = √(4A/π). Then step up to the nearest standard size whose true inside diameter meets or beats it, and confirm the pressure drop per 100 ft stays inside your budget. The calculator above runs all four steps for every size in the series on one keystroke.
What pipe size do I need for a given number of GPM?▼
It depends on the fluid, the material, and how far the water travels — but as a screening answer for schedule-40-type bores: 10 GPM sits comfortably in 3/4 in near 1.8 m/s, 12 GPM needs 1 in copper or larger, and 25 GPM wants 1 1/4 in steel. Read the exact row off the water chart above, or better, let the calculator check velocity and pressure drop for your actual fluid and material instead of trusting a single-number chart.
What velocity should I design for?▼
Start from the fluid. Pressurized water supply is designed between roughly 1.2 and 2.4 m/s, pump suctions at 0.6–1.5 m/s, compressed-air mains at 6–9 m/s, and low-pressure gas is sized by pressure drop with velocity only as a secondary screen. Gravity drains are the exception — depth self-selects, and the goal is a self-cleansing 0.6 m/s floor rather than a cap. The velocity-criteria table above lists each band with its basis.
How do I size compressed air piping?▼
Work in SCFM at the receiver, then check two limits in the pipe itself: keep main-line velocity under about 9 m/s and lose no more than roughly 1 psi per 100 ft. Compressed air at 100 psig is about 7.8 times denser than free air, so a given SCFM figure moves far slower through the pipe than you would expect. The compressed-air table above was computed for exactly those criteria on schedule-40 steel; the calculator reproduces it for other pressures, materials, and budgets.
How do I size natural gas pipe?▼
Use the fuel-gas code tables first. IFGC and the UPC size branches from appliance load in BTU/h, total developed length, and gas specific gravity — and they account for the fittings that a straight-pipe velocity check ignores. A handy screening conversion is CFH ≈ BTU/h ÷ 1,000 for typical supply gas; feed that flow into the calculator as a sanity check, but treat the code table's branch size as the authority, especially near the minimum inlet pressures tankless heaters demand.
What size pipe does a tankless water heater need?▼
Two lines matter. The gas side decides success: a 150–199 kBTU/h unit burns roughly 150–200 CFH, which is why manufacturers commonly accept 3/4 in gas only at short runs and call for 1 in beyond that — always verify against the manual's required inlet pressure and the code tables. The cold-water feed usually lands at 3/4 in to keep the unit's high instantaneous flow under the 2.4 m/s supply ceiling. The calculator above ships a 200 kBTU/h preset that lands on the 1 in gas line.
More Flow Calculators
Every tool linked below runs its own dedicated engine alongside this page — same presets philosophy, same preset-to-result consistency. Open one, or go back to the calculator above and size your line.
Orifice & Valve Flow
Size restrictions instead of lines: flow through orifices, nozzles, and valves from Cv/Kv and ΔP.
Open Channel Flow
Gravity mains and ditches need slope and roughness, not velocity presets — Manning's equation inside.
Tank Fill & Drain Time
Combine the flow your line delivers with storage volume to get fill, drain, and turnover times.
Flow Rate Conversion
Target flow in the wrong units? Convert GPM, CFM, SCFM, and kg/h before sizing.
All Calculators
The full flow toolset on one page, grouped by calculation direction.