Flow Rate Converter

Convert between litres per minute, m³/s, gallons per minute, cubic feet per minute, and m³/h — for plumbing, HVAC, and process engineering.

Flow Rate

m³/s, L/min, gpm, cfm

From

Result

3600

1 m³/s = 3600 m³/h

Popular conversions

What Is a Flow Rate Converter?

A flow rate converter translates volume-per-time between units — litres per minute to gallons per minute, cubic metres per second to cubic feet per minute. Volumetric flow rate is how much fluid passes a point per unit time, central to plumbing, HVAC, irrigation, and process engineering. The SI unit is m³/s, though practical work uses L/min, m³/h, GPM, and CFM.

This converter routes through m³/s. It bridges the metric flow units with the US ones — gallons per minute (GPM) for water and pumps, cubic feet per minute (CFM) for air and ventilation — and keeps US and imperial gallons distinct, since they differ by about 20%.

This is one category of the full Unit Converter — pair it with our percentage calculator or scientific calculator for related everyday maths.

How Flow Rate Conversion Works

Everything routes through m³/s

Each unit has a fixed m³/s factor. The converter normalises your input to m³/s, then projects it into L/min, GPM, CFM, and more.

Flow = volume ÷ time

A tap delivering 9 litres in a minute is 9 L/min. Multiply flow rate by time to get the total volume delivered.

Combines volume and time conversions

Because flow pairs a volume unit with a time unit, its factors fold both together — which is why L/min to m³/h is a clean ×0.06.

Mind which gallon

GPM can mean US or imperial gallons per minute. US (3.785 L) and imperial (4.546 L) flow rates differ by ~20%.

Core Flow Rate Conversion Factors

Multiply to reach m³/s; divide to come back.

L/min → m³/s

÷ 60000

One litre per minute is 1.667 × 10⁻⁵ m³/s (divide by 60,000).

US GPM → L/min

× 3.785412

One US gallon per minute is 3.785 litres per minute.

CFM → m³/h

× 1.699

One cubic foot per minute is 1.699 m³/h, the bridge for ventilation airflow.

How to Use the Flow Rate Converter

1
Enter the flow rate
Type the rate you want to convert — a pump output, a tap flow, a ventilation airflow.
2
Choose the 'from' unit
Pick L/min, m³/s, m³/h, US or imperial GPM, or CFM. Mind which gallon.
3
Choose the 'to' unit
Select the target unit, or swap the two to reverse direction.
4
Read every unit at once
The all-units table shows the flow in L/min, GPM, CFM, and m³/h together.

Key Flow Rate Concepts

Volumetric flow rate

Volume passing a point per unit time, m³/s in SI. The basis for sizing pipes, pumps, fans, and ducts.

GPM

Gallons per minute, the US standard for water flow and pumps. Specify US (3.785 L) or imperial (4.546 L) — they differ ~20%.

CFM

Cubic feet per minute, the US standard for airflow in HVAC and ventilation. A bathroom fan moves ~50–110 CFM.

Flow vs velocity

Flow rate (volume/time) differs from flow velocity (distance/time). Flow rate = velocity × cross-sectional area of the pipe.

Real-World Flow Rate Conversions

🚿

Shower and taps

A 9 L/min shower is 2.4 US GPM. Water-efficiency ratings and plumbing specs flip between L/min and GPM.

💨

Ventilation

A 100 CFM extractor fan moves about 170 m³/h. HVAC airflow is specified in CFM (US) or m³/h (metric).

⛲

Pumps

A pump rated 50 US GPM delivers 189 L/min or 11.4 m³/h. Pump curves convert across these units.

🌊

Rivers and pipes

A pipe flowing 0.1 m³/s carries 6,000 L/min. Large hydraulic flows use m³/s; domestic ones use L/min.

🏭

Process lines

A chemical feed of 2 m³/h is 33.3 L/min. Process engineering mixes m³/h and L/min depending on scale.

🚗

Fuel injection

An injector flowing 250 cc/min delivers 0.25 L/min. Engine tuning works in small flow units like cc per minute.

Best Practices for Flow Rate Conversion

✓Specify US or imperial GPM. A 'GPM' without a system is ambiguous; US and imperial gallons differ by ~20%, so pump and water flows can be off accordingly.
✓Match air to CFM, water to GPM. Ventilation airflow is conventionally CFM (or m³/h); water flow is GPM (or L/min). Use the field's standard to avoid confusion.
✓Don't confuse flow rate with velocity. Flow rate is volume per time; velocity is distance per time. They relate through pipe area — a narrow pipe has high velocity at modest flow.
✓Keep m³/s for hydraulic calculations. Fluid-mechanics formulas use SI m³/s. Convert L/min, GPM, and CFM to m³/s before computing.
✓Watch the time unit. Per-second, per-minute, and per-hour rates differ by factors of 60. Confirm the time basis when comparing two flow figures.

Common Flow Rate Conversion Mistakes

Mixing US and imperial GPM

Treating US GPM as imperial (or vice versa) introduces a ~20% error in pump sizing and water-flow estimates.

Confusing flow rate and velocity

Volume per time and distance per time are different. Pipe sizing needs flow rate; erosion and pressure-drop need velocity.

Dropping the time-unit factor

Per-minute and per-hour rates differ by 60. Converting L/min to m³/h while forgetting the time conversion is a common slip.

Ignoring CFM vs m³/h

Airflow in CFM is ~1.7 m³/h, not 1. Treating them as equal undersizes ventilation by that factor.

Why Flow Rate Conversion Matters

Flow rate sizes pipes, pumps, fans, ducts, and process feeds — get it wrong and a shower trickles, a fan can't clear a room, or a pump is mismatched to its system. The unit landscape is messy: L/min, m³/h, US and imperial GPM, and CFM all coexist, and the US/imperial gallon gap adds a silent ~20% error if unspecified.

Because flow combines a volume with a time, its conversions fold two ratios together and reward care. A converter that routes through m³/s and keeps GPM (US vs imperial) and CFM straight lets a plumber, HVAC tech, or process engineer specify and compare flows across whatever units a spec sheet uses.

Built for plumbers, HVAC technicians, pump and process engineers, and irrigators converting between L/min, GPM, CFM, and m³/h.

Linear unit factors follow the BIPM SI brochure, the NIST Guide to the SI, and ISO 80000. Currency rates load live from open.er-api.com; crypto prices from CoinGecko. See our methodology and editorial policy. Educational only — not certified for regulated trading, settlement, medical, or aerospace use.

Flow Rate Converter FAQs

Divide L/min by 3.785412 for US gallons per minute, or by 4.54609 for imperial GPM. So a 9 L/min shower is about 2.38 US GPM (or 1.98 imperial GPM). Always state which gallon, since the two differ by roughly 20%.

GPM (gallons per minute) measures liquid flow, typically water; CFM (cubic feet per minute) measures gas flow, typically air in ventilation. They measure the same kind of quantity — volume per time — but in different units for different fluids, so they're used in different contexts (plumbing vs HVAC).

Multiply cubic metres per hour by 16.667 to get litres per minute, since 1 m³ = 1,000 L and there are 60 minutes in an hour (1,000 ÷ 60 = 16.667). So 2 m³/h is about 33.3 L/min.

Flow rate is the volume of fluid passing per unit time (e.g. L/min); flow velocity is how fast the fluid moves (e.g. m/s). They relate through the pipe's cross-sectional area: flow rate = velocity × area. The same flow rate gives high velocity in a narrow pipe and low velocity in a wide one.

One cubic metre per hour is about 0.589 CFM, so one CFM is about 1.699 m³/h. This conversion is essential in HVAC, where US equipment is rated in CFM and metric specifications use m³/h.

It uses exact unit definitions (US gallon = 3.785411784 L, imperial gallon = 4.54609 L, 1 ft³ = 0.0283168 m³) combined with exact time factors, and routes every conversion through m³/s at full precision, so the result is exact to your input precision.