Flow Rate Converter

Flow rate is how much fluid moves past a point in a given time. This converter works in volume per time, with liters per minute (LPM) as the base, covering the units you meet around the house and across engineering.

Key relationships:

• 1 GPM = 3.78541 LPM
• 1 m³/h = 16.6667 LPM
• 1 CFM = 28.3168 LPM

Everyday flow rates:

• A slow drip: about 0.5 LPM
• A low-flow bathroom faucet: 1.5 GPM (5.7 LPM)
• A kitchen faucet: about 2.2 GPM (8.3 LPM)
• A shower head: about 2.5 GPM (9.5 LPM)
• A garden hose: 5–10 GPM (19–38 LPM)
• A domestic well pump: about 20 GPM (76 LPM)
• A fire hydrant: 500–1,500 GPM (1,900–5,700 LPM)

Those US figures are not arbitrary. Federal law has capped shower heads at 2.5 GPM since 1994 and kitchen faucets at 2.2 GPM, which is why so many fixtures land on exactly those numbers rather than somewhere near them. WaterSense-labelled shower heads go further, down to 2.0 GPM. If a fixture claims more than the cap it is either an older unit or one sold as something other than a shower head.

Flow against time is the useful step. A rate on its own rarely answers the question; multiply it out and it does. A 2.5 GPM shower run for eight minutes is 20 gallons, so a household of four showering daily moves about 29,000 gallons a year through the water heater. The converter above prints litres per hour and cubic metres per day alongside the rate for exactly that reason: water bills are charged by volume, not by how fast it arrived.

GPM (gallons per minute) and LPM rule water and plumbing. CFM (cubic feet per minute) is the air-world unit, used for HVAC airflow, ventilation sizing, and air-compressor ratings. They all describe the same idea in different volumes.

Two cautions. First, the US gallon and the UK (Imperial) gallon are different sizes, so a “GPM” figure means about 20 percent more flow in Britain than in America, which matters when reading specs across the Atlantic. Second, for gases, volumetric flow shifts with pressure and temperature because gas compresses. That’s why compressor ratings often quote “standard” CFM (SCFM), measured at a fixed reference condition, so two machines can actually be compared on equal terms.