The free Pipe Flow & Pressure Drop Calculator
Calculate pipe flow velocity, Reynolds number, friction factor (Colebrook), head loss, pressure drop and pump power from flow rate, diameter, length.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Illustration. Open the tool for the real thing.
See it in action
Sample input: Density ρ (kg/m³) — used for “Custom” = 998.2; Dynamic viscosity μ (Pa·s) — “Custom” = 0.001002; Flow rate = 10; Inside diameter (mm) = 100
What is the Pipe Flow & Pressure Drop Calculator?
Sizing a pipe or pump starts with the pressure drop for a given flow. This calculator uses the Darcy–Weisbach equation, the engineering standard: Δp = f·(L/D)·ρv²/2 plus minor losses ΣK·ρv²/2 and any elevation change. Enter the flow rate (L/s, L/min, m³/h, US gpm or m³/s), the inside diameter, the length, the pipe material (a roughness table from drawn tubing and PVC to riveted steel) or a custom roughness, the fluid (water at five temperatures, seawater, air or glycerin, or your own density and viscosity), the sum of fitting loss coefficients, the elevation rise and the pump efficiency.
It returns the velocity, the Reynolds number and the flow regime, the friction factor from 64/Re for laminar flow or the Colebrook–White equation for turbulent flow (with the Swamee–Jain explicit formula as a cross-check), the head loss, the pressure drop in kPa and psi and per metre, and the pump power. For water pipes a Hazen–Williams comparison is shown and warnings flag velocities above 3 m/s, transitional flow and very low velocities. For 10 L/s of 20 °C water in 100 m of 100 mm commercial steel pipe the pressure drop is about 15.8 kPa.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
Laminar and turbulent friction factors, Swamee–Jain cross-check.
Presets for water, seawater, air, glycerin and common pipe roughness.
Fittings ΣK and height change included.
Hydraulic power from pressure and flow, with efficiency.
AZRS tools are free to open and use.
It opens in your browser, so there is nothing to download.
Used for
Pick one to see how it fits.
How it compares
A plain look at this tool next to the usual alternative.
| This engineering calculator | Desktop software | |
|---|---|---|
| Install | Nothing to install | Usually an app or program to install |
| Account | No signup | Depends on the product |
| Cost | Free to use | Free or paid, depends on the product |
| Where it runs | In your browser tab | On your computer |
Questions people ask
What is the Colebrook equation?
The implicit equation for turbulent friction factor, solved iteratively here.
Is Hazen–Williams better?
It is simpler and only valid for water at normal temperatures.
Does it handle gases?
Incompressible flow only; fine for air at low pressure drops.
Is it free?
Yes.
How do I use the Pipe Flow & Pressure Drop Calculator?
1. Enter flow rate, diameter, length and roughness. 2. Choose the fluid or enter its properties. 3. Add fitting losses and elevation rise. 4. Read pressure drop, velocity and pump power.
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Velocity, Reynolds number, friction factor, head loss, pressure drop and pump power for. Free to use.
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