US gallons per minute to liters per minute

An American shower head is legally capped at 2.5 gallons per minute — 9.46 liters per minute in any metric plumbing code. The conversion runs through 3.785411784, the exact liter content of the US gallon, and it is the most common pump-rating translation in the plumbing world: American pump curves say GPM, the rest of the world says L/min, and the same pump gets rated both ways.

By EnginStack Engineering Team | Verified by engineers, built on NIST metrology standards About →
US gallons per minute
5 liters per minute
5 US gallons per minute = 18.92705892 liters per minute 5 liters per minute = 1.32086026 US gallons per minute

Constants verified against NIST Special Publication 811 (Guide for the Use of the International System of Units) and the 1959 International Yard and Pound Agreement. All values are exact — none are rounded approximations.

US gallons per minute to liters per minute

The US gallon is defined as exactly 231 cubic inches, which makes it exactly 3.785411784 liters, so one gallon per minute is exactly 3.785411784 liters per minute. The number carries full precision because every step in its derivation is a definition: 231 in³ × (2.54 cm)³ per liter. Plumbing fixtures, swimming pool pumps, and irrigation systems all cross this factor, and because the constant is exact, there is never a reason to round it in a spec.

liters per minute = US gallons per minute × 3.785411784
1 GPM = 3.785411784 L/min — the 231 in³ gallon
The factor is exact by definition.

Common US gallons per minute to liters per minute Conversions

US gallons per minuteliters per minuteContext
1 GPM3.79 L/minThe definitional anchor.
2.5 GPM9.46 L/minThe US legal shower-head cap.
5 GPM18.9 L/minA high-flow shower or small pump.
10 GPM37.9 L/minA pool circulation pump.
100 GPM378.5 L/minA fire truck's pump.

Engineering Context

This is the reciprocal of the L/min to GPM page. The 3.785411784 anchor comes from the gallons to liters volume converter, and the flow rate hub collects all ten flow converters. Pool pumps and fire flows also connect to the pressure family, since pump head and flow are traded against each other on every pump curve.

More: L/min to GPM · GPM to m³/h · gal to L · Flow Rate Hub

Related Unit Converters

L Min To Gpm Gpm To M3 H Gallons To Liters Flow Rate Converters

Frequently Asked Questions

How many liters per minute is 1 GPM?

Exactly 3.785411784. The US gallon is 231 in³ = 3.785411784 L by definition, so a gallon per minute is 3.785411784 liters per minute.

Why is the US shower head limited to 2.5 GPM?

The US Energy Policy Act of 1992 capped shower heads at 2.5 GPM at 80 psi to save water and energy. That is 9.46 L/min — the number this converter produces for the legal limit.

How do I convert GPM to L/min quickly?

Multiply by 3.785 for a mental estimate, or by 3.785411784 for exact work. Dividing by 0.2641720524 gives the same answer.