Flow Rate Converter
Convert between litres per minute, cubic metres per hour, GPM and CFM.
What the Flow Rate Converter does
Flow rate is volume per unit time. Water systems typically use L/min or GPM; air handling and ventilation use CFM; and civil engineering uses m³/s for rivers and large channels.
Formula
Convert to litre per second, then divide by the target unit's factorResult = Value × (from factor ÷ to factor)
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Value | number | Yes | — |
| From | one of 8 options | Yes | — |
| To | one of 8 options | Yes | — |
How to use it
- Choose From and To.
- Enter Value.
- Select Calculate.
Worked example
Convert a 40 L/min pump to gallons per minute.
- Value
- 40
- From
- Litre per minute
- To
- US GPM
40 ÷ 3.7854 = 10.57 GPM.
Reading the result
- For a sense of scale: a shower runs 6–12 L/min, a garden hose 12–18 L/min, and a domestic mains supply rarely exceeds 30 L/min.
Assumptions and limitations
- Gallons here are US gallons. An imperial gallon per minute is about 1.2 times a US one.
- Gas volumes depend on pressure and temperature, so a flow in CFM describes the volume at the stated conditions rather than a fixed mass of air.
Common mistakes
- Confusing volumetric flow with mass flow. A cubic metre of air and a cubic metre of water move very different masses.
- Comparing a pump rating against a pipe capacity without accounting for pressure drop, which limits real throughput well below either figure.
Frequently asked questions
What flow rate does a typical shower use?
Around 9–12 L/min (2.5–3 GPM). Low-flow heads cut that to about 6 L/min.