U.S. sprinkler and fire-pump sheets list flow in U.S. gallons per minute (gpm), while many metric and international specifications use liters per second (L/s). Using the standard conversion, 1 L/s = 15.850323 gpm (1 U.S. gallon = 3.785411784 L), so gpm ÷ 15.850323 = L/s and L/s × 15.850323 = gpm. This page is a free browser converter either direction. It is for learning and quick checks—not a substitute for the criteria adopted by your authority having jurisdiction, manufacturer data, a sealed hydraulic calculation, or review by a licensed design professional. It is not a design stamp and not a PE seal.
How the conversion is used
- Confirm the source unit (U.S. gpm on most U.S. sheets; L/s on many metric specifications). Do not mix U.S. and imperial gallons.
- Convert with 1 L/s = 15.850323 gpm: QL/s = Qgpm / 15.850323, or Qgpm = QL/s × 15.850323.
- Keep the same flow meaning (sprinkler demand, hose allowance, rated pump flow, or test flow) when you switch units.
- After units match, continue with friction loss, velocity, or pump sketches in consistent units.
Free calculator
Educational approximation only. Uses 1 L/s = 15.850323 U.S. gpm. Nothing you enter leaves your browser. For liters per minute see GPM to LPM; for cubic meters per hour see GPM to m³/h. Segment friction sketches live in the Sprinkler Pipe Friction Loss workbook.
Worked example
A 500 gpm hose stream allowance: 500 / 15.850323 ≈ 31.55 L/s. Conversely, a 63 L/s pump rating × 15.850323 ≈ 998.6 gpm. Always confirm the source unit and check the result against the adopted edition, manufacturer data, and AHJ—not this page alone.
Next steps: check pipe velocity with the free sprinkler pipe velocity calculator, sketch friction with the friction loss calculator, and run full segment tables in the Sprinkler Pipe Friction Loss workbook ($29). For pump and tank sizing, use the Fire Pump & Tank Sizing workbook ($49).