Convert mass flow rate between kg/s, kg/h, lb/s, lb/h and tonnes per hour.
Fluids • 8 units
All 8 units on the Mass Flow Rate Converter are defined against the Kilogram/second (kg/s), so each result is one conversion factor away from a single reference rather than the end of a chain of roundings.
The conversion this page is most often opened for is ready before you type anything: 1 kg/s = 7,936.63391 lb/h. Change either side and every row in the table recalculates with it.
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The page's default pair spans the gulf between laboratory and plant units: 1 kg/s is about 7,937 lb/h. Process instrumentation rarely reports in kilograms per second, because the numbers become inconveniently small, so tonnes per hour and pounds per hour dominate the control room while the underlying models are written in SI. Moving cleanly between them is most of the day-to-day work this quantity involves.
Standard volumetric units are mass flow rates wearing a disguise. Normal cubic metres per hour and standard cubic feet per minute both fix a reference pressure and temperature, so the figure quoted is really an amount of substance rather than a volume. The catch is that the reference conditions are not universal — different industries and standards bodies anchor to different temperatures — so a flow copied between a gas-industry document and a compressed-air specification can shift by several percent without a single number appearing to change.
How the measurement was made determines how much the density assumption matters. A Coriolis meter senses mass directly by measuring the twist a flowing fluid imparts to a vibrating tube, so its output needs no density input at all. An orifice plate infers mass flow from a differential pressure and is only as good as the density figure fed to it, which is why a gas metering error usually traces back to pressure and temperature compensation rather than to the plate. A turbine or positive-displacement meter measures volume alone, and converting its output to mass is an assumption rather than a measurement.
Quick reference — 1 Kilogram/second (kg/s) is equal to:
| Gram/second | g/s | 1,000 |
| Kilogram/hour | kg/h | 3,599.997120 |
| Kilogram/minute | kg/min | 59.999880 |
| Pound/second | lb/s | 2.204623 |
| Pound/hour | lb/h | 7,936.633910 |
| Tonne/hour | t/h | 3.599997 |
| US ton/hour | ton/h | 3.968317 |
8 units of mass flow rate, each a fixed multiple of the kg/s. The table spans 7,937:1, from lb/h (0.000125998 kg/s) to kg/s (1 kg/s). Conversion is one multiplication into the base unit and one division out of it, with no lookup table and no approximation.
value_to = value_from × (factor_from ÷ factor_to)1 kg/s = 1 kg/s1 g/s = 0.001 kg/s1 kg/h = 0.000277778 kg/s1 kg/min = 0.0166667 kg/s1 lb/s = 0.453592 kg/s1 lb/h = 0.000125998 kg/s1 t/h = 0.277778 kg/s1 ton/h = 0.251996 kg/swhere:
Assumptions: Factors are exact definitions. Full double precision is carried internally and rounding is applied only for display.
Result25 kg/s = 198416 lb/h
Mass flow rate is mass passing a point per unit time, in kilograms per second (kg/s). It is preferred over volumetric flow wherever density is not constant, because mass is conserved through a process while volume is not.
Gases make the difference stark. A cubic metre of air at 10 bar contains roughly ten times the mass of a cubic metre at atmospheric pressure, so a volumetric reading taken before a compressor and one taken after describe completely different quantities of gas. Combustion, chemical dosing and refrigeration are all specified in mass terms for exactly this reason, and the pounds-per-hour and tonnes-per-day units here reflect how process plants actually report it.