Volumetric Flow Rate Converter

How to convert volumetric flow rate units

Enter a flow rate, pick the unit it is in, and pick the unit you want. Cubic meters per second and per hour, liters per second and per minute, US gallons per minute and cubic feet per second all update from one entry.

The cubic meter per second is the internal base and each factor is exact, so a pump curve in m3/h and a spec sheet in gpm can be compared without a chain of rounded steps.

• Confirm whether the gallons in your source are US or imperial.
• Type the flow rate in the Value box, for example 20.
• Pick the From unit, for example Liter per minute (L/min).
• Pick the To unit, for example Gallon per minute (gal/min).
• Read the result and use the table to compare against a pump curve in m3/h.

Reading a pump curve in the wrong units

Pump manufacturers publish a curve of flow against head, and the horizontal axis is printed in whatever unit the market expects: m3/h in most of Europe, L/min for smaller circulators, US gpm across North America, and L/s in parts of the water industry. Comparing two pumps means putting both curves in the same unit first, and that is the entire job this page does.

The factor that trips people is between m3/h and gpm: one cubic meter per hour is 4.4028675393 US gallons per minute, so a 10 m3/h pump is a 44 gpm pump. Reading a European curve as if the axis were gpm undersizes the duty point by a factor of four and a half, which is the sort of mistake that only shows up once the system is running.

• 1 m3/h = 16.6666666667 L/min = 4.4028675393 US gpm.
• 1 L/s = 60 L/min = 3.6 m3/h.
• 1 US gpm = 3.785411784 L/min = 0.22712471 m3/h.

Volumetric flow is not mass flow, and not velocity

Every unit here measures a volume passing a point per unit of time. Mass flow, in kg/s or lb/h, is a different quantity, and converting between them needs the density of the fluid. Water at room temperature is convenient because a liter is almost exactly a kilogram, but that coincidence disappears for oil, gas, or slurry, so this page deliberately has no mass units.

Velocity is a third quantity again. Flow divided by the internal cross-sectional area of the pipe gives the mean velocity, which is what determines whether a line is running quietly or eroding its own elbows. The converter has no pipe diameter field, so compute the area yourself, keep both figures in SI units, and divide.