Flow Rate Converter

Convert between volumetric flow rate units — GPM, liters per minute, cubic meters per hour, CFM, and more.

From

Value

Unit

Result

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Enter a value to convert

GPM

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L/min

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m³/h

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CFM

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Current value in every unit — click any card to set as target

Reference: All Units Relative to 1 m³/s

Unit	Symbol	In m³/s	1 m³/s =

1 GPM = 0.0000631 m³/sgallons per minute (US) 1 L/min = 0.0000167 m³/sliters per minute 1 L/s = 0.001 m³/sliters per second 1 m³/h = 0.000278 m³/scubic meters per hour 1 CFM = 0.000472 m³/scubic feet per minute 1 GPM ≈ 3.785 L/minquick GPM-to-LPM shortcut

🛡️ Verified Precision

SI Standard Compliant

This flow rate conversion tool uses exact SI-derived coefficients through a cubic-meters-per-second (m³/s) base, with the US gallon (3.78541 liters) as the reference for GPM. Real-world flow figures (shower heads, garden hoses, pumps) are approximate and vary by fixture and manufacturer — verify against a spec sheet for engineering or code-compliance use.

4 min read 3 steps 6 terms 3 examples 6 FAQs value_from × factor_from = m³/s; m³/s ÷ factor_to = value_to

Flow rate — how much liquid or gas moves past a point per unit of time — gets measured in a confusing mix of units depending on the industry and country.

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Walk-through

How to Use This Calculator

3 steps

Enter your flow rate value

Type the number you want to convert into the value field. It can be any positive number — a faucet rating, a pump spec, or an HVAC duct requirement.

Pick the units to convert between

Choose the unit your value is currently in ('From') and the unit you want to see it in ('To') — GPM, L/min, L/s, m³/h, CFM, or ft³/s. The result updates instantly as you change either dropdown.

Check the Reference and Common tabs

Switch to Reference to see your value expressed in every supported unit at once, or open Common to browse typical flow rates for faucets, hoses, and pumps and load one straight into the converter.

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Reference

Formula & Methodology

1 formula

Convert through a common base unit

value_from × factor_from = m³/s; m³/s ÷ factor_to = value_to

Every unit is defined by a fixed factor that converts it to cubic meters per second (m³/s), the SI base unit for volumetric flow rate. To convert between any two units, the calculator first converts the input to m³/s, then divides by the target unit's factor. Factors used: 1 GPM (US) = 0.0000631 m³/s, 1 L/min = 0.0000167 m³/s, 1 L/s = 0.001 m³/s, 1 m³/h = 0.000278 m³/s, 1 CFM = 0.000472 m³/s, 1 ft³/s = 0.0283168 m³/s.

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Glossary

Key Terms Explained

6 terms

Flow rate The volume of a fluid or gas that passes a given point per unit of time. It's a rate, not a total volume — 10 GPM means 10 gallons pass every minute, indefinitely, not 10 gallons total.

GPM (Gallons Per Minute) A US customary unit of volumetric flow rate, common in plumbing, pump, and irrigation specs in the United States. This calculator uses the US liquid gallon (3.78541 liters), not the UK imperial gallon.

LPM (Liters Per Minute) The metric equivalent of GPM, used almost everywhere outside the US. 1 GPM converts to roughly 3.785 LPM, which is why the two units are so often paired on spec sheets.

CFM (Cubic Feet per Minute) A US customary unit of volumetric flow rate used almost exclusively for air and gas flow — HVAC ductwork, exhaust fans, air compressors — rather than liquids.

Volumetric flow The general term for measuring how much volume of a substance moves through a cross-section over time, as opposed to mass flow rate (which measures weight or mass moved per unit time).

Discharge An engineering and hydrology term for the volumetric flow rate of a fluid — often used interchangeably with 'flow rate' in pump curves, pipe sizing, and stream-gauging contexts.

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Scenarios

Real-World Examples

3 worked examples

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Homeowner

Checking a garden hose against a shower head

Value 10 From GPM

10 GPM converts to about 37.85 L/min — roughly 4 times the flow of a standard 2.5 GPM shower head. That's typical for a garden hose at moderate water pressure, so a 10 GPM reading on a hose spec is normal, not a leak.

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HVAC technician

Reading a bathroom exhaust fan's rated CFM

Value 80 From CFM

80 CFM converts to about 135.9 m³/h — a common rating for a bathroom exhaust fan sized for an 8×10 ft room. Building codes often specify a minimum CFM per square foot, so converting to m³/h helps when cross-checking against metric ventilation standards.

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Pool owner

Matching a replacement pump to the original spec

Value 60 From GPM

A 60 GPM pump equals about 227.1 L/min or 13.6 m³/h. When a European-made replacement pump lists its output in L/min or m³/h, converting to GPM lets you confirm it matches (or exceeds) your original US-spec pump before buying.

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Deep Dive

Understanding Flow Rate Conversions

3 chapters · 4 min read

Flow rate — how much liquid or gas moves past a point per unit of time — gets measured in a confusing mix of units depending on the industry and country. This converter translates between the six most common ones so you can compare a US pump spec against a metric duct rating without doing the math by hand.

Why flow rate has so many units

Plumbing and irrigation in the US default to gallons per minute (GPM), while most of the rest of the world uses liters per minute (L/min) or liters per second (L/s). HVAC and air-handling equipment almost always uses cubic feet per minute (CFM) for air and gas flow, since air is measured by volume rather than liquid gallons. Industrial and metric engineering specs often use cubic meters per hour (m³/h) instead. None of these units is wrong — they're just conventions that took hold in different industries and regions, which is exactly why a converter is useful when specs from different sources need to be compared side by side.

How the conversion works

This calculator converts every unit through a single common base — cubic meters per second (m³/s), the SI unit for volumetric flow rate. Your input value is first converted to m³/s using that unit's fixed factor, then converted from m³/s into the target unit. This two-step approach means adding a new unit only requires one conversion factor, and it guarantees that converting A → B gives the same answer as converting A → m³/s → B, with no rounding surprises from unit-pair-specific shortcuts.

Where this calculator falls short

This tool converts flow rate units directly — it does not account for pressure, pipe diameter, fluid viscosity, or friction losses, all of which affect the actual flow rate a real system delivers. A pump rated for 60 GPM at the manufacturer's test conditions may deliver less once installed with your specific pipe run and elevation change. For pump sizing, pipe sizing, or code-compliance ventilation calculations, use the converted number as a starting reference and consult a spec sheet, engineer, or the relevant plumbing/HVAC code for the final figure.

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Questions

Frequently Asked Questions

6 questions

How do I convert GPM to LPM (liters per minute)?+

Multiply the GPM value by 3.78541 to get liters per minute, since 1 US gallon equals 3.78541 liters. For example, 10 GPM × 3.78541 ≈ 37.85 L/min. This calculator does that conversion (and the reverse) instantly — just select GPM as the 'From' unit and L/min as the 'To' unit.

What is CFM and when is it used instead of GPM?+

CFM (cubic feet per minute) measures the volumetric flow rate of air or gas, not liquid. It's the standard unit for HVAC equipment, exhaust fans, air compressors, and ventilation system specs in the US. GPM, by contrast, is used almost exclusively for liquid flow like water or fuel. If you're sizing ductwork or comparing fan output, you want CFM; if you're sizing a water pump or irrigation line, you want GPM.

Why would I need cubic meters per hour (m³/h)?+

m³/h is the standard metric unit for flow rate on equipment manufactured outside the US, and it's common in industrial process specs, European pump datasheets, and international engineering standards. If you're comparing a US-spec pump (rated in GPM) against an imported one (rated in m³/h), converting both to the same unit lets you compare their actual output directly.

How do I size a pump correctly using flow rate conversions?+

Start by finding your required flow rate in whatever unit your application specifies (e.g. GPM for a pool, CFM for ventilation), then convert any candidate pump's rated output into that same unit before comparing. Remember that a pump's rated GPM or CFM is typically measured at zero head/static pressure — real-world output drops as pipe length, elevation, and fittings add resistance, so match units first, then consult the pump's full performance curve for your specific installation.

Is the US gallon the same as the imperial gallon?+

No. This calculator uses the US liquid gallon (3.78541 liters), which is standard in North American plumbing and pump specs. The UK/imperial gallon is larger — about 4.54609 liters — and is still used in some older British and Commonwealth equipment. If you're converting a UK-spec flow rate, confirm which gallon the manufacturer means before trusting a GPM-based conversion.

Why does this calculator convert everything through m³/s?+

Cubic meters per second (m³/s) is the SI base unit for volumetric flow rate, so using it as a common intermediate means every supported unit only needs one conversion factor (to and from m³/s) rather than a separate factor for every possible pair of units. This keeps the math consistent and makes it easy to verify: converting GPM to CFM, for instance, produces the same result whether you go GPM → CFM directly or GPM → m³/s → CFM.

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GPM	L/min	Context
1.5 GPM	5.68 L/min	Kitchen faucet
2 GPM	7.57 L/min	Low-flow shower head
2.5 GPM	9.46 L/min	Standard shower head
10 GPM	37.85 L/min	Garden hose (low end)
17 GPM	64.35 L/min	Garden hose (high end)
40 GPM	151.4 L/min	Small pool pump
60 GPM	227.1 L/min	Sump pump
100 GPM	378.5 L/min	Large pool pump

Flow Rate Converter

Real-World Reference

Quick Conversion Table

🛡️ Verified Precision

How to Use This Calculator

Enter your flow rate value

Pick the units to convert between

Check the Reference and Common tabs

Formula & Methodology

Key Terms Explained

Real-World Examples

Homeowner

HVAC technician

Pool owner

Understanding Flow Rate Conversions

Why flow rate has so many units

How the conversion works

Where this calculator falls short

Frequently Asked Questions

Get a branded PDF of your results

Flow Rate Converter

Real-World Reference

Quick Conversion Table

🛡️ Verified Precision

How to Use This Calculator

Enter your flow rate value

Pick the units to convert between

Check the Reference and Common tabs

Formula & Methodology

Key Terms Explained

Real-World Examples

Understanding Flow Rate Conversions

Why flow rate has so many units

How the conversion works

Where this calculator falls short

Frequently Asked Questions

Get a branded PDF of your results

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