GPM to m³/h calculator

U.S. fire-flow and sprinkler sheets usually list flow in gallons per minute (gpm), while many metric notes and international product sheets use cubic meters per hour (m³/h). Using the U.S. liquid gallon, 1 gpm = 0.227124707 m³/h, so gpm × 0.227125 = m³/h and m³/h × 4.402867 = 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

1. Confirm which unit your source report or datasheet uses (gpm on most U.S. fire-flow sheets; m³/h on many metric / international sheets).
2. Convert with the U.S. liquid gallon factor: Q_m³/h = Q_gpm × 0.227125, or Q_gpm = Q_m³/h × 4.402867.
3. Keep the same flow meaning (rated pump flow, test flow, or demand) when you switch units.
4. After units match, continue with friction loss, hydrant, tank duration, or pump sketches in consistent units.

Free calculator

Educational approximation only. Uses 1 gpm = 0.227124707 m³/h (U.S. liquid gallons). Nothing you enter leaves your browser. For L/min conversions see GPM to LPM and LPM to GPM. For CFS see GPM to CFS. Multi-segment paths live in the Sprinkler Pipe Friction Loss workbook.

Worked example

A demand of 500 gpm: 500 × 0.227125 ≈ 113.6 m³/h. Conversely, 100 m³/h × 4.402867 ≈ 440.3 gpm. Always confirm whether the source used U.S. liquid gallons (this page) versus another gallon definition, and check the result against the adopted edition, manufacturer data, and AHJ—not this page alone.

Next steps: convert to L/min with the free GPM to LPM calculator, convert to CFS with the GPM to CFS calculator, sketch supply with the hydrant flow test calculator, size segment losses with the friction loss calculator or Hazen-Williams friction loss calculator, and build multi-segment paths in the Sprinkler Pipe Friction Loss workbook ($29). Pump and tank tables live in the Fire Pump & Tank Sizing workbook ($49).