EngineeringFormulaEngineering Unit Conversions
Clean reference pages for the engineering unit pairs that come up most often when comparing US customary specs with SI or international data sheets. Each conversion includes the exact factor, a live converter, a reference table, and practical notes about where the unit pair is used.
10
conversion pages
8
unit families
Exact
tested conversion factors
Before converting
- Pressure conversions keep the same reference point: psi gauge becomes kPa gauge unless atmospheric pressure is added separately.
- Temperature conversions are not pure multipliers; Fahrenheit to Celsius needs both an offset and a scale factor.
- Mass and force are different quantities, so lb-to-kg is not the same as lbf-to-newton.
How to use this index
- Use these pages when a datasheet, code note, or calculator input is in a different unit system.
- Convert first, then run the relevant calculator with one consistent unit system.
- If a conversion depends on context, such as gauge vs absolute pressure, read that pair's note before reusing the number.
Conversion index
All unit conversions
HVAC equipment specced by US manufacturers is rated in CFM; specs from EU or ISO-standard manufacturers use m³/h. This conversion comes up whenever a duct, fan, or exhaust rating needs to be compared across both.
Duct and conveyor velocity in US HVAC and manufacturing practice is almost always quoted in feet per minute (FPM); most engineering calculations and non-US references use meters per second instead.
US pressure gauges, tire specs, and hydraulic ratings read in psi; most engineering calculations and international datasheets use kPa. This is one of the most commonly looked-up unit conversions in mechanical and fluid work.
Bar is the standard pressure unit across most of Europe and on many hydraulic and pneumatic component datasheets, while psi remains standard in US practice - this conversion comes up constantly when reading imported equipment specs.
Motor and engine power is rated in horsepower on US nameplates and in kilowatts almost everywhere else. It's the single most-searched power conversion for anyone comparing US and international equipment.
Nearly every material weight, shipping spec, or load rating in US practice is given in pounds, while essentially all engineering calculation and international specifications use kilograms.
US automotive and hand-tool torque specs - torque wrenches, bolt-tightening specs - are almost always given in pound-feet; engineering calculations and most of the rest of the world use newton-meters.
Unlike every other pair on this page, this is an affine conversion, not a pure multiplier - it needs both a scale factor and an offset (°C = (°F − 32) × 5/9), which is why a naive unit-multiplier approach gets it wrong.
Machined part tolerances and fastener sizes in US practice are dimensioned in inches, often down to thousandths; the same parts from metric-standard manufacturers are dimensioned in millimeters.
Pump and pipe flow specs from US manufacturers are rated in US gallons per minute; European and most other international pump curves are rated in liters per minute.