This mass flow rate converter changes a mass flow between kilograms per second, grams per second, kilograms per hour, tonnes per hour, pounds per second, pounds per minute and pounds per hour. The SI unit is kg/s. The factors are exact because the pound is defined as 0.45359237 kg: 1 lb/h = 0.45359237 kg/h, and 1 kg/h ≈ 2.20462 lb/h.
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How to use the mass flow rate converter
- Enter the flow, for example 1,500 from a steam meter in kg/h.
- In the mass flow rate converter, choose its unit and the target unit.
- Read the mass flow rate converter result: 1,500 kg/h ≈ 3,306.9 lb/h.
For kg/h to lb/h, multiply by 2.20462; for lb/h to kg/h, multiply by 0.453592.
What is mass flow rate?
Mass flow rate is the mass of material passing a point per unit time, measured in kilograms per second in SI. It is used for fuel, steam, gas and bulk solids, where mass is a better measure than volume.
Conversion formula
The mass flow rate converter stores every unit as a multiple of the base unit, the kilogram per second (kg/s). To convert:
value in target unit = value × (factor of source unit ÷ factor of target unit)
where each factor is the size of the unit in kilograms per second.
Common mass flow rate conversions
| From | To | 1 unit equals |
|---|---|---|
| pound per minute (lb/min) | kilogram per second (kg/s) | 0.007559873 kg/s |
| kilogram per hour (kg/h) | pound per hour (lb/h) | 2.204623 lb/h |
| tonne per hour (t/h) | kilogram per second (kg/s) | 0.2777778 kg/s |
Mass flow rate converter worked example
Convert 25 kilograms per hour to pounds per hour:
- Factor of kg/h = 0.00027777778 kg/s
- Factor of lb/h = 0.00012599788 kg/s
- 25 × 0.00027777778 ÷ 0.00012599788 = 55.11557 lb/h
Mass flow rate unit reference
| Unit | Symbol | Group | Equals (kg/s) |
|---|---|---|---|
| Kilogram per Second | kg/s | SI | 1 |
| Gram per Second | g/s | Metric | 0.001 |
| Kilogram per Hour | kg/h | Metric | 0.0002777777778 |
| Tonne per Hour | t/h | Metric | 0.2777777778 |
| Pound per Second | lb/s | US/Imperial | 0.45359237 |
| Pound per Minute | lb/min | US/Imperial | 0.007559872833 |
| Pound per Hour | lb/h | US/Imperial | 0.0001259978806 |
Reverse factors for each mass flow rate unit
The reference table gives each unit in kilogram per seconds. To go the other way, divide by that factor; the list below does the division for you.
- Gram per Second (g/s), Metric: 1 g/s = 0.001 kg/s, so 1 kg/s = 1,000 g/s.
- Kilogram per Hour (kg/h), Metric: 1 kg/h = 0.0002777778 kg/s, so 1 kg/s = 3,600 kg/h.
- Tonne per Hour (t/h), Metric: 1 t/h = 0.2777778 kg/s, so 1 kg/s = 3.6 t/h.
- Pound per Second (lb/s), US/Imperial: 1 lb/s = 0.4535924 kg/s, so 1 kg/s = 2.204623 lb/s.
- Pound per Minute (lb/min), US/Imperial: 1 lb/min = 0.007559873 kg/s, so 1 kg/s = 132.2774 lb/min.
- Pound per Hour (lb/h), US/Imperial: 1 lb/h = 0.0001259979 kg/s, so 1 kg/s = 7,936.641 lb/h.
Steam boiler capacity in lb/h and kg/h
Boiler output is often stated in boiler horsepower, defined as evaporating 34.5 lb of water per hour from and at 212 °F:
| Boiler horsepower | Steam (lb/h) | Steam (kg/h) |
|---|---|---|
| 1 | 34.5 | 15.6 |
| 10 | 345 | 156.5 |
| 50 | 1,725 | 782.4 |
| 100 | 3,450 | 1,564.9 |
| 250 | 8,625 | 3,912.2 |
| 500 | 17,250 | 7,824.5 |
Steam tables and process sheets then use these mass flows directly.
Mass flow to volume flow
Mass flow equals density times volume flow: ṁ = ρ × Q. Water at about 1,000 kg/m³ flowing at 10 L/min carries about 0.167 kg/s (600 kg/h). For gases, density changes with pressure and temperature, so state the conditions. Use the volumetric flow rate converter and the density converter for the inputs.
Fuel burn as mass flow
Engines and burners are often rated by fuel mass flow. A generator that burns 20 L/h of diesel, at about 0.832 kg/L, uses 16.6 kg/h. The mass flow rate converter shows that as about 4.6 g/s or 36.7 lb/h. Aircraft and boiler data usually quote fuel in lb/h or kg/h because mass, not volume, sets the energy released. Fuel volume changes with temperature, but mass does not.
To go from volume flow to mass flow, multiply by density. To go back, divide. Use the density at the actual fuel temperature when accuracy matters.
For gases, the same idea applies but density changes a lot with pressure, so mass flow is the safer number to compare.
Related converters and calculators
Related flow tools:
- Flow rate converter: gpm, L/min, m³/h
- Molar flow rate converter: mol/s and kmol/h
- Mass flux converter: kg/(m²·s)
- Density converter: kg/m³ and g/cm³
- Weight converter: kg and lb
Sources
NIST Special Publication 811, Appendix B; BIPM: SI Brochure.
Questions about this calculator
What is the SI unit of mass flow rate?
Kilogram per second (kg/s).
How do I convert kg/h to lb/h?
Multiply by 2.20462. For example, 500 kg/h = 1,102.3 lb/h.
How do I convert lb/h to kg/h?
Multiply by 0.453592. For example, 10,000 lb/h = 4,535.9 kg/h.
How do I convert kg/s to lb/s?
Multiply by 2.20462. For example, 3 kg/s = 6.61 lb/s.
How do I convert mass flow to volume flow?
Divide by density: Q = ṁ ÷ ρ. 2 kg/s of water at 1,000 kg/m³ is 0.002 m³/s, or 2 L/s.
What is a boiler horsepower?
The capacity to evaporate 34.5 lb of water per hour from and at 212 °F, about 9.81 kW.
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
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