This free engineering unit converter handles conversions across eight categories — length, area, volume, pressure, temperature, flow rate, force, and power — between metric (SI) and imperial/US customary units. Enter a value and pick the from/to units; the result updates instantly. It's a quick reference for design calculations, spec reviews, and translating between drawings that mix unit systems.
The converter covers the eight quantities engineers convert most often:
• Length — mm, cm, m, km, in, ft, yd, mi • Area — mm², m², ft², acres, hectares • Volume — mL, L, m³, gal (US), ft³ • Pressure — Pa, kPa, bar, psi, atm, mmHg, inH₂O • Temperature — °C, °F, K • Flow rate — L/s, m³/h, GPM, CFM • Force — N, kN, lbf, kgf • Power — W, kW, hp, BTU/hr
Pick a category, choose the input and output units, and read the converted value.
Select the quantity you want to convert, enter the known value, and choose the source and target units. Most conversions are simple ratios (multiply by a factor). Temperature is the exception — it uses offset formulas, not a single ratio (see the FAQ). Results are shown to engineering precision; round to the significant figures appropriate for your application.
Unit errors are a classic and costly source of engineering mistakes. Mixing imperial and metric values — or confusing US gallons with imperial gallons, or pounds-force with pounds-mass — has caused real-world failures. Converting explicitly with a tool, and carrying units through every calculation, guards against these errors. Always confirm which gallon, ton, or BTU definition a spec uses.
Eight: length, area, volume, pressure, temperature, flow rate, force, and power — each with the common metric (SI) and imperial/US customary units used in engineering practice.
Yes. Every category includes both SI and imperial/US customary units, so you can convert in either direction — for example meters to feet, kPa to psi, L/s to GPM, or kN to lbf.
Temperature is not a simple ratio because the scales have different zero points. Celsius to Fahrenheit is °F = °C × 9/5 + 32; Celsius to Kelvin is K = °C + 273.15. The converter applies these offset formulas automatically rather than multiplying by a single factor.
The converter uses standard conversion factors to high precision. For design work, round the result to the number of significant figures justified by your input data and the tolerance of your application — extra decimal places do not add real accuracy if the input is approximate.