Flow Rate Converter

Frequently Asked Questions

How is flow rate converted?

All units pivot through cubic metres per second. E.g. 1 US gpm = 6.309×10⁻⁵ m³/s, 1 CFM = 4.719×10⁻⁴ m³/s, 1 L/min = 1.667×10⁻⁵ m³/s.

US gallons vs UK gallons?

They differ ~20%: 1 US gal = 3.785 L, 1 UK (imperial) gal = 4.546 L. US gpm and UK gpm are not interchangeable - pick the right one.

What is CFM used for?

Cubic feet per minute measures air/gas flow in HVAC, compressors, and ventilation. The converter relates it to L/s and m³/h for cross-discipline work.

Does this assume a fluid?

It is a pure volumetric-rate conversion (volume ÷ time), independent of the fluid. Mass flow would additionally require density.

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How This Calculator Works

Volumetric flow rate measures how much volume passes a point per unit of time. The SI base unit is the cubic metre per second (m³/s), and every other flow unit is a fixed multiple of it, so conversion pivots cleanly through that base: result = amount × (m³PerSecondFrom ÷ m³PerSecondTo). The stored factors come from exact volume and time definitions: 1 L/s = 0.001 m³/s; 1 L/min = 0.001 ÷ 60 m³/s; 1 m³/h = 1 ÷ 3600 m³/s; 1 US gallon = 0.0037854118 m³ so 1 US gpm = that ÷ 60; 1 imperial (UK) gallon = 0.00454609 m³ so 1 UK gpm differs from US gpm by about 20%; 1 ft³ = 0.028316846592 m³ so 1 CFM = that ÷ 60; and 1 oil barrel = 0.158987294928 m³, giving 1 bbl/day over 86,400 seconds. Because litres and gallons are volume units, this is strictly volumetric flow - not mass flow (kg/s), which additionally requires fluid density.

Worked Example

A pump is rated at 50 US gpm and you need litres per minute. Step 1: 50 × (0.0037854118 ÷ 60) = 0.0031545 m³/s. Step 2: 0.0031545 ÷ (0.001 ÷ 60) ≈ 189.3 L/min. Reverse it: a 10 L/s irrigation line is 10 × 0.001 = 0.01 m³/s = 36 m³/h, or about 158.5 US gpm. An HVAC duct moving 400 CFM equals 400 × (0.028316846592 ÷ 60) ≈ 0.1888 m³/s ≈ 679.6 m³/h. The US-vs-UK gallon gap matters: 100 US gpm is only about 83.3 UK gpm.

Where You Use This

Plumbers and pump engineers size systems quoted in gpm (US), L/min, or m³/h depending on region. HVAC designers convert duct airflow between CFM and m³/h or L/s. Water utilities and irrigation planners work in L/s and m³/h. The oil and gas industry uses barrels per day for well and pipeline throughput. Process and chemical engineers normalise vendor specs to a single base before sizing valves and meters.

Common Mistakes

US vs UK gallon: a US gallon (3.785 L) is about 17% smaller than an imperial gallon (4.546 L); mixing them skews flow by ~20%.

Volumetric vs mass flow: m³/s is volume per time; converting to kg/s needs the fluid density and is not done here.

Per-minute vs per-second: forgetting the ÷60 (or ×60) is the single most common flow-conversion error.

CFM at different conditions: actual (ACFM) and standard (SCFM) cubic feet differ by air density - this tool converts the geometric volume only.

Barrel ambiguity: here a barrel is the 42-US-gallon oil barrel; beer and dry barrels have different volumes.

Reference Factor Table

1 m³/s = 1000 L/s = 3600 m³/h = 15850.32 US gpm

1 L/s = 60 L/min = 3.6 m³/h = 15.85032 US gpm = 2.118880 CFM

1 US gpm = 3.785412 L/min = 0.2271247 m³/h = 0.8326742 UK gpm

1 UK gpm = 4.546090 L/min = 1.200950 US gpm

1 CFM = 1.699011 m³/h = 28.31685 L/min = 0.4719474 L/s

1 bbl/day = 0.1589873 m³/day = 0.0066245 m³/h = 0.0291606 US gpm

Frequently Asked Questions

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