Engineering calculators for pipe flow & fluid mechanics
Every calculator on this page is free and works instantly in your browser, alongside the Moody Chart Calculator. Use them to check whether flow is laminar or turbulent, work out the Darcy friction factor, calculate pressure drop, or size a pump.
Friction factor & flow regime
Moody Chart Calculator
Find the Darcy friction factor for any pipe flow using the Colebrook-White equation. Includes an interactive Moody diagram.
Main ToolReynolds Number Calculator
Determine whether flow is laminar, transitional, or turbulent. Essential first step before using the Moody Chart.
Swamee-Jain Calculator
Get friction factor instantly using the explicit Swamee-Jain approximation. Compare results against the Colebrook-White equation.
Laminar Flow Friction Factor Calculator
For laminar flow (Re < 2300), friction factor is simply 64/Re. Calculate it here instantly.
Pressure, head loss & flow
Pressure Drop Calculator
Calculate pressure loss in a pipe using the Darcy-Weisbach equation. Enter friction factor, pipe dimensions, and fluid properties.
Head Loss Calculator
Compute friction head loss in meters of fluid. Use this to size pipes and pumps in water supply and HVAC systems.
Pipe Flow Velocity Calculator
Find fluid velocity from flow rate and pipe diameter. The starting point for Reynolds number and pressure drop calculations.
Volumetric Flow Rate Calculator
Convert between velocity and flow rate for a given pipe diameter. Results in m³/s, L/s, and m³/h.
Pump Power Calculator
Estimate the power needed to drive a pump given flow rate, head, fluid density, and efficiency. Results in W, kW, and hp.
Hazen-Williams Calculator
Head loss in water pipes from the Hazen-Williams equation, with C roughness coefficients by pipe material.
Pipe properties & fluid properties
Pipe Roughness Calculator
Look up absolute roughness for common pipe materials (steel, cast iron, PVC, copper) and calculate relative roughness ε/D.
Relative Roughness Calculator
Calculate ε/D from pipe roughness height and diameter. This is the input you need for the Moody Chart and Colebrook equation.
Kinematic Viscosity Calculator
Convert dynamic viscosity and density to kinematic viscosity (ν = μ/ρ). Required for Reynolds number calculations.
Not sure where to start?
If you're new to pipe flow analysis, this is the typical workflow an engineer follows:
- Find fluid velocity: use the Pipe Flow Velocity Calculator if you know the flow rate and pipe diameter.
- Get the fluid properties: use the Kinematic Viscosity Calculator to convert dynamic viscosity and density into the kinematic viscosity Reynolds number needs.
- Calculate Reynolds number: use the Reynolds Number Calculator to find Re and determine the flow regime.
- Get relative roughness: use the Pipe Roughness Calculator to find ε/D for your pipe material.
- Find friction factor: enter Re and ε/D into the Moody Chart Calculator to get the Darcy friction factor.
- Cross-check your answer: if flow is laminar, confirm with the Laminar Flow Friction Factor Calculator; if it is turbulent, compare against the Swamee-Jain Calculator.
- Calculate pressure drop or head loss: use the Pressure Drop Calculator or Head Loss Calculator.
- Size your pump: use the Pump Power Calculator to find the required motor power.
Learn more: guides & articles
How to read the Moody chart
A visual, step-by-step guide to finding friction factor directly from the chart.
Reynolds number explained
What it means, how to calculate it, and why it matters for pipe flow.
Kinematic vs dynamic viscosity
What each one means and why Reynolds number uses the kinematic value.
Pipe pressure drop: the complete guide
Major and minor losses, friction factor, and worked Darcy-Weisbach examples.
Pipe roughness: a practical guide
Roughness values for every common pipe material and how aging affects them.
Darcy-Weisbach vs Hazen-Williams
Which pressure drop method should you use and when?