Flow Rate Converter

1. Enter the value you want to convert.
2. Choose the from unit.
3. Choose the to unit.
4. Read the result and the conversion rate.

Here is what each result means:

A volumetric flow rate is how much fluid passes a point in a given time. It is the number behind a tap's output, a pump's capacity, a ventilation fan's airflow and a river's discharge. Because different trades and regions use different units, the same flow can be written as litres per minute, cubic metres per hour, gallons per minute or cubic feet per minute.

All these units share the same idea, a volume divided by a time, so they differ only by the size of the volume unit and the length of the time unit. Litres per minute is common for taps and small pumps, cubic metres per hour for larger water systems, gallons per minute for plumbing and pools, and cubic feet per minute, or CFM, for airflow and ventilation.

This converter bridges every unit through litres per second. It multiplies your value by the litres per second in its unit, then divides by the litres per second in the target unit. Because each unit has a fixed value, the conversions are exact and never change.

As with other volume units, the gallon comes in two sizes. A US gallon is about 3.785 litres and an imperial gallon about 4.546, so US and UK gallons per minute are different, and the converter keeps them separate to avoid confusion.

It converts through litres per second, a convenient base.

1. Your value is multiplied by its unit's value in litres per second.
2. That gives the flow in litres per second, the common base.
3. Dividing by the target unit's value gives the result.

To convert the volumes or distances involved, see the volume calculator and the length converter.

Convert 60 litres per minute to litres per second.

Result: 60 L/min is 1 L/s, since there are 60 seconds in a minute. The same flow is 3.6 cubic metres per hour, or about 15.85 US gallons per minute.

Every unit has a fixed value in litres per second.

The metric units convert neatly by tens and sixties, while the imperial ones carry the odd sizes of the gallon and the cubic foot. CFM is the standard for airflow, so it appears on fans and ventilation systems rather than water flows.

Different jobs favour different units.

Matching the unit to the field makes a flow figure meaningful. A 10 litre-per-minute tap, a 100 cubic-metre-per-hour main and a 400 CFM fan are all flow rates, each in the unit its trade finds natural.

The Two Units

The ratio between the from-unit and to-unit sets the result; each has a fixed value in litres per second.

The Time Unit

Per second, per minute and per hour differ by factors of 60 and 3,600.

Which Gallon

US and imperial gallons differ in size, so their flow units differ too.

Plumbing and Pumps

Match a pump rated in one unit to a requirement in another.

Ventilation

Convert airflow between CFM and cubic metres per hour.

Water Systems

Move between litres per minute and cubic metres per hour for supply and irrigation.

1. Mixing US and UK Gallons

The imperial gallon is larger, so US and UK gallons per minute are different.

2. Slipping a Time Factor

Per minute and per second differ by 60, and per hour by 3,600. Keep the time unit straight.

3. Confusing Airflow and Water Flow

CFM is common for air; litres per minute for water. Both are volumetric flow, but the fields differ.

4. Wrong Direction

Check which unit is the from and which is the to; swapping them inverts the result.

5. Mixing Mass and Volume Flow

This converter handles volumetric flow, not mass flow such as kilograms per second.

Conversions use fixed factors relative to litres per second.

1 litre per second. There are 60 seconds in a minute, so 60 litres per minute divided by 60 is 1 litre per second.

Multiply cubic metres per hour by about 16.67. One cubic metre is 1,000 litres, and one hour is 60 minutes, so 1 m3/h is about 16.67 litres per minute.

Cubic feet per minute, the standard unit for airflow from fans and ventilation. One CFM is about 0.472 litres per second.

The imperial gallon is about 20 percent larger than the US gallon, so a UK gallon per minute is a larger flow than a US gallon per minute.

Multiply US gallons per minute by about 3.785, or UK gallons per minute by about 4.546. So 10 US GPM is about 37.85 litres per minute.

Litres per minute or cubic metres per hour for metric work, and gallons per minute where imperial units are used. Match the unit to your field.

Volume flow, the volume passing per unit time. Mass flow, such as kilograms per second, also depends on the fluid's density and is not covered here.

Work out the flow you need, convert it to the pump's unit, and check the pump meets it at the required pressure. This tool handles the unit conversion.

No. The calculation runs in your browser and nothing you enter is stored or sent anywhere, unless you choose Save, which keeps the result only on this device.

• Volumetric flow rate (Wikipedia).
• Gallon (Wikipedia).
• Cubic foot per minute (Wikipedia).