Flow Rate Converters

Flow rate is volume divided by time — the number that decides whether a pump works, a pipe is big enough, or an HVAC system moves enough air. The units split along the same two axes as the volume and time families behind them: the metric world flows in liters per minute and cubic meters per hour, the American world in gallons per minute and cubic feet per minute. Every factor on this page is exact — the US gallon is 231 in³ by definition, the foot is 0.3048 m by the 1959 agreement, and the liter is a cubic decimeter. None of the constants here is rounded, and all of them chain back to the same anchors the rest of the site uses.

By EnginStack Editorial Team | Reviewed against NIST, BIPM and primary-source documentation About →

Liters per Minute & Gallons per Minute — Pumps & Fixtures

L/min to GPM 1 L/min = 0.2642 GPM. A kitchen faucet at 8 L/min is 2.1 GPM. Every European pump spec meets an American one through this factor. × 0.26417 GPM to L/min 1 GPM = 3.7854 L/min. A 5 GPM shower head flows 18.9 L/min. The exact reciprocal of the US gallon. × 3.7854

Liters per Minute & Cubic Meters per Hour — Municipal & Industrial

L/min to m³/h 1 L/min = 0.06 m³/h. A 100 L/min booster pump delivers 6 m³/h. The ×0.06 factor is pure decimal — 60 minutes in an hour, 1,000 L in a cubic meter. × 0.06 m³/h to L/min 1 m³/h = 16.667 L/min. A 12 m³/h circulation pump flows 200 L/min. The reverse of the same decimal chain. × 16.667

Gallons per Minute & Cubic Meters per Hour — Crossing the Atlantic

GPM to m³/h 1 GPM = 0.2271 m³/h. A 60 GPM fire pump moves 13.6 m³/h. The US gallon chained through the liter to the cubic meter. × 0.22712 m³/h to GPM 1 m³/h = 4.4029 GPM. A 10 m³/h irrigation pump is 44 GPM. The reciprocal transatlantic flow. × 4.4029

Liters per Second & Liters per Minute — Fire & High Flow

L/s to L/min 1 L/s = 60 L/min. A 4 L/s fire hydrant flows 240 L/min. The ×60 rule is exact — seconds to minutes. × 60 L/min to L/s 1 L/min = 0.0167 L/s. A 30 L/min lab pump is 0.5 L/s. The reverse of the same definition. ÷ 60

Gallons per Minute & Cubic Feet per Minute — HVAC & Air

GPM to CFM 1 GPM = 0.1337 CFM. The 231 in³ gallon over the 1,728 in³ cubic foot. Chiller and cooling-tower water vs air comparisons. × 0.13368 CFM to GPM 1 CFM = 7.4805 GPM. The exact reciprocal — a cubic foot holds 7.48 US gallons. × 7.4805

Exact conversion factors

Flow rate mixes a volume unit with a time unit, and the two traditions differ about both. The table gives the exact factors for the five units that appear on pump curves and air-handling schedules.

From	To	Exact factor	Basis
1 US gallon per minute	liters per minute	3.785411784	Exact, the size of a US gallon
1 US gallon per minute	cubic meters per hour	0.22712470704	Exact, 3.785411784 liters × 60 ÷ 1,000
1 US gallon per minute	cubic feet per minute	0.133680555556	Exact, 231 divided by 1,728
1 cubic foot per minute	liters per second	0.4719474432	Exact, 28.316846592 liters ÷ 60
1 cubic foot per minute	cubic meters per hour	1.69901079552	Exact, 0.3048 cubed × 60
1 liter per second	liters per minute	60	Exact
1 cubic meter per hour	liters per minute	16.6666666667	Exact, 16.6666666667
1 US gallon per minute	liters per second	0.0630901964	Derived, 0.0630901964
1 cubic foot per minute	US gallons per minute	7.48051948052	Derived, 7.480519480519
1 liter per minute	cubic meters per hour	0.06	Exact, 0.06

Defining values and exact constants

One US gallon per minute is 3.785411784 L/min and 0.22712470704 m³/h. Pumps are quoted in all three on the same datasheet, and the conversion is one factor.
One cubic foot per minute is exactly 7.4805194805 US gallons per minute, because a cubic foot holds 1,728 cubic inches and a US gallon holds 231.
One cubic foot per minute is 1.69901079552 m³/h. The figure is 0.3048 cubed and then multiplied by 60, both exact.
One liter per second is 15.8503231415 US gallons per minute, the conversion needed when a European plumbing specification meets an American one.
A shower head limited to 2.5 gpm delivers 9.46 L/min, while a European head rated at 6 L/min is 1.585 gpm, a difference of about 36 percent in water used.

Frequently asked questions

How do you convert GPM to L/min?

Multiply by 3.785411784. A 5 gpm pump delivers 18.93 liters per minute. The factor is the exact size of a US gallon, so it is a definition rather than a measurement.

What is CFM in liters per second?

One CFM is 0.4719474432 L/s. It follows from one cubic foot being 28.316846592 liters and one minute being 60 seconds, and both of those are exact.

Why do HVAC engineers use CFM and plumbers use GPM?

Because the two trades reference different volumes. Air flow is derived from a cubic foot, water flow from a gallon, and the two volumes were fixed independently.

Is one cubic meter per hour the same as one liter per minute?

No, one cubic meter per hour is 16.667 liters per minute. A cubic meter is 1,000 liters and an hour is 60 minutes, so the hourly unit moves more than sixteen times as much water per minute.

What's on this page

Ten converters covering the five flow units that actually show up in engineering work — liters per minute (SI process), gallons per minute (US pumps and fixtures), cubic meters per hour (municipal and industrial), liters per second (fire and high-flow), and cubic feet per minute (HVAC and compressed air). Flow rate is a derived quantity: volume ÷ time. That means every factor here is the product of a volume constant from the volume pages and the 60-second minute from the time family. The GPM↔CFM pair is the only one that carries a non-decimal constant (0.1336805556), because it divides the 231 in³ gallon by the 1,728 in³ cubic foot. If you're converting mass flow — kilograms per hour, pounds per minute — that's density × volume flow, and the density hub has the mass side. Flow rate tells you how much moves; density tells you what it weighs.