Flow Converter
Convert volumetric flow rate between cubic meters, liters, gallons, barrels, cubic feet and more per second, minute, hour or day. Pick a source and a target unit, enter a value and read the result instantly.
Select two units to see the conversion factor.
This converter handles volume per time only. For kilograms or pounds per time, use the Flow - Mass Converter; turning volume into mass needs the fluid density.
Flow Formula
Every volumetric flow unit is a volume unit divided by a time unit, so each one is a fixed multiple of one reference unit, the cubic meter per second (m³/s). To convert, multiply the value by the size of the source unit in m³/s, then divide by the size of the target unit in m³/s. The volumes (liter, US and UK gallon, cubic foot, barrel, acre-foot) are exact definitions and the time bases are 60 s, 3,600 s, 86,400 s and, for acre-foot per year, 365 days. The converter keeps full double precision until the final result is displayed.
What Is Volumetric Flow Rate?
Volumetric flow rate is the volume of fluid that passes a point in a unit of time. It describes how fast a pump fills a tank, how much water a pipe delivers, how much air a fan moves or how much oil a well produces. The SI unit is the cubic meter per second (m³/s), although liters per second, liters per minute and cubic meters per hour are far more convenient for everyday pipes and pumps.
Flow rate equals the cross-sectional area of the flow multiplied by its average velocity (Q = A × v). Because the quantity is a volume, it does not say how heavy the fluid is. A flow of 10 L/min of water and 10 L/min of oil are the same volumetric flow, but the mass flow differs because the densities differ.
Different industries have settled on different units. Plumbing and pumps in the United States use gallons per minute (GPM), HVAC and ventilation use cubic feet per minute (CFM), oil and gas use barrels per day, water-resource planning uses acre-feet per year, and laboratories use milliliters per minute. A flow converter lets you move between all of them without a table.
Supported Units
This converter supports the following 50 volumetric flow units. The last column shows how many cubic meters per second one unit equals. The US gallon (3.785411784 L) and the UK or imperial gallon (4.54609 L) are different, as are the US and UK fluid ounce, so check which one your source uses. The barrel is the 42-US-gallon oil barrel, and the acre-foot per year uses a 365-day year.
| Unit | Symbol | Value in m³/s |
|---|---|---|
| Cubic meter per second | m³/s | 1 |
| Cubic meter per day | m³/d | 1.157407407e-5 |
| Cubic meter per hour | m³/h | 0.0002777777778 |
| Cubic meter per minute | m³/min | 0.01666666667 |
| Cubic centimeter per day | cm³/d | 1.157407407e-11 |
| Cubic centimeter per hour | cm³/h | 2.777777778e-10 |
| Cubic centimeter per minute | cm³/min | 1.666666667e-8 |
| Cubic centimeter per second | cm³/s | 1e-6 |
| Liter per day | L/d | 1.157407407e-8 |
| Liter per hour | L/h | 2.777777778e-7 |
| Liter per minute | L/min | 1.666666667e-5 |
| Liter per second | L/s | 0.001 |
| Milliliter per day | mL/d | 1.157407407e-11 |
| Milliliter per hour | mL/h | 2.777777778e-10 |
| Milliliter per minute | mL/min | 1.666666667e-8 |
| Milliliter per second | mL/s | 1e-6 |
| Gallon (US) per day | gal (US)/d | 4.381263639e-8 |
| Gallon (US) per hour | gal (US)/h | 1.051503273e-6 |
| Gallon (US) per minute | gal (US)/min | 6.30901964e-5 |
| Gallon (US) per second | gal (US)/s | 0.003785411784 |
| Gallon (UK) per day | gal (UK)/d | 5.261678241e-8 |
| Gallon (UK) per hour | gal (UK)/h | 1.262802778e-6 |
| Gallon (UK) per minute | gal (UK)/min | 7.576816667e-5 |
| Gallon (UK) per second | gal (UK)/s | 0.00454609 |
| Kilobarrel (US, oil) per day | kbbl/d | 0.001840130728 |
| Barrel (US, oil) per day | bbl/d | 1.840130728e-6 |
| Barrel (US, oil) per hour | bbl/h | 4.416313748e-5 |
| Barrel (US, oil) per minute | bbl/min | 0.002649788249 |
| Barrel (US, oil) per second | bbl/s | 0.1589872949 |
| Acre-foot per year | ac·ft/y | 3.911345248e-5 |
| Acre-foot per day | ac·ft/d | 0.01427641016 |
| Acre-foot per hour | ac·ft/h | 0.3426338438 |
| Hundred cubic foot per day | CCF/d | 3.2774128e-5 |
| Hundred cubic foot per hour | CCF/h | 0.000786579072 |
| Hundred cubic foot per minute | CCF/min | 0.04719474432 |
| Fluid ounce (US) per hour | fl oz (US)/h | 8.214869323e-9 |
| Fluid ounce (US) per minute | fl oz (US)/min | 4.928921594e-7 |
| Fluid ounce (US) per second | fl oz (US)/s | 2.957352956e-5 |
| Fluid ounce (UK) per hour | fl oz (UK)/h | 7.892517361e-9 |
| Fluid ounce (UK) per minute | fl oz (UK)/min | 4.735510417e-7 |
| Fluid ounce (UK) per second | fl oz (UK)/s | 2.84130625e-5 |
| Cubic yard per hour | yd³/h | 0.0002123763494 |
| Cubic yard per minute | yd³/min | 0.01274258097 |
| Cubic yard per second | yd³/s | 0.764554858 |
| Cubic foot per hour | ft³/h | 7.86579072e-6 |
| Cubic foot per minute | ft³/min | 0.0004719474432 |
| Cubic foot per second | ft³/s | 0.02831684659 |
| Cubic inch per hour | in³/h | 4.551962222e-9 |
| Cubic inch per minute | in³/min | 2.731177333e-7 |
| Cubic inch per second | in³/s | 1.6387064e-5 |
How to Use the Flow Converter
- Type the flow rate in the value box. Decimals and scientific notation such as 0.0025 or 2.5e-3 are accepted.
- Choose the From unit and the To unit.
- The result appears instantly, or press Convert Now. Very large or very small results are shown in scientific notation.
- Use Swap Units to reverse the conversion, Copy Result to copy the answer, open Show this value in all units for a full list, and Clear to start again.
Step-by-step by hand
- Find the size of each unit in the common base unit (m³/s): 1 gal (US)/min = 6.30901964e-5 m³/s and 1 m³/h = 0.0002777777778 m³/s.
- Divide the source size by the target size to get the conversion factor: 6.30901964e-5 ÷ 0.0002777777778 = 0.227124707, so 1 gal (US)/min = 0.227124707 m³/h.
- Multiply by your value: 250 gal (US)/min × 0.227124707 = 56.78117676 m³/h.
Flow rate cannot be negative, so only zero and positive numbers are accepted.
Common Flow Conversions
- Pump rating: a pump rated at 100 gal (US)/min delivers 378.5411784 L/min, which is 22.7124707 m³/h.
- Fan or duct airflow: 1,000 ft³/min equals 1,699.010796 m³/h or 471.9474432 L/s.
- Water supply: 5 L/s equals 18 m³/h and 79.25161571 gal (US)/min.
- Oil production: 1,000 bbl/day equals 158.9872949 m³/day.
- Irrigation and reservoirs: 1 acre-foot per year equals 3.379402295 m³/day.
- Laboratory pump: 0.5 mL/s equals 1.8 L/h.
- US versus UK gallons: 10 gal (UK)/min is 12.00949926 gal (US)/min.
Gallons per Minute Conversion – Common Values
Quick reference for frequently used values
| Gal (US)/min | Liter/min | m³/hour | Liter/second | ft³/min |
|---|---|---|---|---|
| 1 | 3.785411784 | 0.227124707 | 0.0630901964 | 0.1336805556 |
| 5 | 18.92705892 | 1.135623535 | 0.315450982 | 0.6684027778 |
| 10 | 37.85411784 | 2.27124707 | 0.630901964 | 1.336805556 |
| 25 | 94.6352946 | 5.678117676 | 1.57725491 | 3.342013889 |
| 50 | 189.2705892 | 11.35623535 | 3.15450982 | 6.684027778 |
| 100 | 378.5411784 | 22.7124707 | 6.30901964 | 13.36805556 |
| 250 | 946.352946 | 56.78117676 | 15.7725491 | 33.42013889 |
| 500 | 1,892.705892 | 113.5623535 | 31.5450982 | 66.84027778 |
| 1,000 | 3,785.411784 | 227.124707 | 63.0901964 | 133.6805556 |
Where and Why This Conversion Is Used
- Pumps and plumbing: catalogues quote flow in GPM, L/min or m³/h depending on the market, so selecting or comparing pumps often needs a conversion.
- HVAC and ventilation: airflow targets are written in CFM in North America and in m³/h or L/s elsewhere.
- Water and wastewater: treatment plants and utilities report capacity in m³/day, million gallons per day or L/s.
- Oil and gas: production and pipeline volumes are quoted in barrels per day or thousand barrels per day.
- Irrigation and agriculture: pump and canal capacities are compared with field water needs, sometimes expressed in acre-feet.
- Laboratories and medicine: syringe pumps and chromatography flow rates use mL/min, mL/h or L/h.
For flow in mass units see the Flow - Mass Converter, and for amount of substance per time use the Flow - Molar Converter. Plain volume conversions are available in Liters to Gallons.