Grams per Second to Kilograms per Hour Converter
Common Conversions
| g/s | kg/h |
|---|---|
| 0.1 | 0.36 |
| 0.5 | 1.8 |
| 1 | 3.6 |
| 2 | 7.2 |
| 5 | 18 |
| 10 | 36 |
| 25 | 90 |
| 50 | 180 |
| 100 | 360 |
| 1000 | 3600 |
Why this conversion matters in chemistry
Continuous-flow API manufacture is a place this matters. A microreactor pump set to 0.5 g/s of a coupling-partner stock produces 1.8 kg/hr of throughput — the per-hour figure that aggregates into the campaign-total kilogram tonnage for a Phase II clinical-supply batch. The multiplier of 3.6 kg/hr per g/s follows from the 3600 s/hr × 0.001 kg/g cancellation. You use it when an instrument-side per-second flow rate needs to be in the per-hour mass-balance form a process-development summary expects.
Formula
Where the factor comes from
The mass side and the time side of this factor come from entirely different traditions, and neither contributes a measurement. Mass is straightforward decimal prefix work: a kilogram is 10³ grams, so grams per second become kilograms per second on division by a thousand. Time is not decimal at all. The second is defined by fixing the cesium-133 hyperfine transition frequency at 9192631770 Hz; the minute and the hour are not SI units but are accepted for use with SI, the hour set at exactly 60 × 60 = 3600 seconds. Rendering a per-second rate as per-hour therefore multiplies by 3600. Combine them: 3600 ÷ 1000 = 3.6, exact, with a piece of sexagesimal counting sitting inside an otherwise metric number. The reciprocal, 1 ÷ 3.6 = 0.2777…, repeats, which is why the other direction is the awkward one to write.
Precision and significant figures
3.6 is exact, so the figures belong entirely to the flow measurement, and those are rarely as good as the display implies. A Coriolis meter holds a few tenths of a percent of reading across most of its span but degrades sharply below roughly a tenth of full scale, where zero drift starts to dominate; sizing the meter to the rate matters more than any digit you write down. Thermal mass meters for gases carry a gas-dependent calibration and read wrong for anything but the gas they were set up on. And a pump rate is a setpoint, not a measurement — a syringe or peristaltic pump asked for 0.500 g/s deserves a gravimetric check before its number is treated as data.
Worked Examples
The conversion anchor — a typical small-scale flow-reactor feed rate.
A pilot-plant reagent-dosing rate — the step beyond bench-scale flow chemistry.
The reverse anchor — about how many grams per second make a kilogram per hour.
Common mistakes
Volumetric flow converted as if it were mass
Most pumps are set in mL/min rather than g/s, and the bridge between the two is the density of the fluid at the temperature it is actually being pumped at. Multiplying a volumetric setpoint by 3.6 yields a number with the right units and the wrong meaning; for an organic solvent near 0.8 g/mL that is a twenty percent error.
An instantaneous rate reported as hourly output
Multiplying a g/s reading by 3.6 gives what the line would deliver in an hour if it held that rate for the whole hour. Start-up ramps, priming volumes, filter loading and hold-up mean it did not. For a material balance, integrate the flow across the run rather than scaling a single reading.
Rounding the reciprocal to 0.28
Going the other way divides by 3.6, equivalently multiplying by 0.2777…, and the repeating decimal invites truncation. Using 0.28 introduces about eight parts per thousand — trivial on one reading, a visible discrepancy once it has been applied across a day of continuous operation and set against a weighed total.