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Engineering Units Conversion Cheat Sheet
The conversions instrument engineers use daily, on one page: volume and mass flow, pressure, temperature, power and energy, viscosity, density and length.
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A one page A4 sheet to print, pin up in the workshop or keep on your phone. Everything on it is also shown below.
Download PDF A4 · 62 KBVolume flow
| From | To | Multiply by |
|---|---|---|
| m³/h | US gpm | 4.4029 |
| m³/h | L/s | 0.27778 |
| m³/h | ft³/min | 0.58858 |
| US gpm | m³/h | 0.22712 |
| bbl/day | m³/h | 0.0066245 |
| L/min | m³/h | 0.06 |
Mass flow
| From | To | Multiply by |
|---|---|---|
| kg/h | lb/h | 2.20462 |
| t/h | kg/s | 0.27778 |
| kg/s | kg/h | 3600 |
Pressure
| From | To | Multiply by |
|---|---|---|
| bar | kPa | 100 |
| bar | psi | 14.5038 |
| psi | kPa | 6.89476 |
| mbar | mmH₂O | 10.197 |
| inH₂O | Pa | 249.09 |
| mmHg | Pa | 133.322 |
| atm | bar | 1.01325 |
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Temperature
| °C to °F | °F = °C × 1.8 + 32 |
| °F to °C | °C = (°F − 32) ÷ 1.8 |
| °C to K | K = °C + 273.15 |
| Difference | 1 K = 1 °C = 1.8 °F |
Power and energy
| From | To | Multiply by |
|---|---|---|
| kW | BTU/h | 3412.14 |
| kW | hp (metric) | 1.35962 |
| kW | hp (mechanical) | 1.34102 |
| kWh | MJ | 3.6 |
| kcal | kJ | 4.1868 |
Viscosity and density
| From | To | Multiply by |
|---|---|---|
| cP | mPa·s | 1 |
| cSt | mm²/s | 1 |
| cP | cSt | ÷ density (g/cm³) |
| g/cm³ | kg/m³ | 1000 |
| lb/ft³ | kg/m³ | 16.0185 |
Length and area
| From | To | Multiply by |
|---|---|---|
| inch | mm | 25.4 |
| ft | m | 0.3048 |
| in² | mm² | 645.16 |
| AWG 18 | mm² | 0.823 |
Gas reference conditions
- Normal (Nm³): 0 °C, 1.01325 bar a (common).
- Standard (Sm³): 15 °C, 1.01325 bar a (common).
- US standard (SCF): 60 °F, 14.696 psia.
- Always state the basis.
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Frequently Asked Questions
Is psi gauge or absolute?
Conversions are the same; add psig or psia to state the reference.
Why do inH₂O values differ between sources?
They depend on the water reference temperature (4 °C, 60 °F or 68 °F).
Which hp should I use?
Mechanical hp (745.7 W) is common in the US; metric hp (735.5 W) in Europe and India.
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