Unit Converter

About Our Unit Converter

The AI Calculator unit converter handles 17 categories of measurement, with more than 200 individual units between them — covering everything from the everyday (length in feet, mass in kilograms, temperature in °F vs °C) to the technical (energy in BTU vs joules vs kWh, pressure in psi vs bar vs Pa vs mmHg, flow rate in gpm vs L/s vs m³/h, dynamic viscosity in cP vs Pa·s). Each conversion is performed against the SI base units defined by the BIPM, with conversion factors taken from NIST SP 811 and ISO 80000. Where industry-specific units are involved (the foot-pound used by petroleum engineers vs the more precise pound-foot of physics texts), the calculator uses the most widely cited convention and labels it clearly.

17 Conversion Categories Supported

• Length — metres, kilometres, miles, feet, inches, yards, nautical miles, light-years.
• Mass & Weight — kg, g, lb, oz, tonnes (metric & short), stones, slugs.
• Temperature — Celsius, Fahrenheit, Kelvin, Rankine. Handles the offset arithmetic correctly.
• Volume — litres, m³, US/UK gallons, fluid ounces, cups, barrels (oil & dry).
• Area — m², hectares, acres, sq ft, sq miles.
• Speed — m/s, km/h, mph, knots, ft/s.
• Pressure — Pa, kPa, MPa, bar, psi, atm, mmHg/torr, inHg.
• Energy — J, kJ, kWh, BTU, calories (thermochemical & nutritional), erg, eV.
• Power — W, kW, MW, HP (mechanical, metric, electric), BTU/h, ft·lb/s.
• Force — N, kN, lbf, kgf, dyne.
• Time — seconds through to centuries, including sidereal day where relevant.
• Angle — radians, degrees, gradians, arcminutes, arcseconds.
• Flow rate, Frequency, Density, Data storage (B/KB/KiB/…), and Currency-style numerical conversions.

A Note on the Two Most-Misused Conversions

Temperature is not a simple multiplicative scaling. Going from °F to °C requires the offset: T(°C) = (T(°F) − 32) × 5/9. From °C to K is just T(K) = T(°C) + 273.15. The converter handles both, including Rankine (T(R) = T(°F) + 459.67) which still appears in some US thermodynamics texts. Pressure unit confusion is the second classic trap: gauge vs absolute. The converter performs the unit math (psi to bar, bar to Pa) but does not change the reference frame. If your input is psig (gauge), the output is also relative to atmospheric; if you need absolute, add 14.696 psi (or 1.01325 bar) explicitly.

When the Converter Saves You Time

The converter is most useful in mixed-units engineering work: a US specification calling for 150 psi at 5 gpm needs to be matched against an imported European pump rated for 10 bar at 19 L/min — one quick conversion confirms compatibility. In nutrition, the converter handles calories (food-label kilocalories) vs scientific calories (1/1000 of the same). In aviation, knots (nautical miles per hour) need to be cross-checked against indicated airspeed in km/h. In electrical work, watts vs horsepower vs BTU/h all describe the same power, and the converter snaps between them.

Frequently Asked Questions

How accurate are the conversions?
To 15 significant figures internally, displayed to a sensible precision (typically 6–10 sig figs depending on the unit pair). For metrology-grade work, consult NIST SP 811 directly — some traditional units (the US fluid gallon vs the UK Imperial gallon) differ by ~20% and the wrong choice silently corrupts results.

Does the converter support compound units like kWh/m³?
Yes for energy/volume combinations and similar engineering compounds. For arbitrary user-defined compound units, calculate intermediate steps separately.

Why does the converter sometimes show different results than Wikipedia?
Conversion factors do shift over time as definitions are tightened (the SI definition of the kilogram changed in 2019). The converter uses the current definitions. For historical work, use period-correct factors.

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