Accuracy, formulas and methodology

ExactUnit uses deterministic conversion factors in your browser. International definitions include 1 lb = 0.45359237 kg, 1 inch = 0.0254 meter, and 1 international foot = 0.3048 meter. The U.S. liquid gallon is 3.785411784 liters; it is not the imperial gallon.

Definitions and reference sources

Our definitions follow the International System of Units (SI) and recognized U.S. customary measurement factors. See NIST's Guide to SI conversion factors and the BIPM SI Brochure.

How we calculate

For linear units, the original value is converted into a common base unit and then into the target unit. Temperature uses offset formulas, such as °F = (°C × 9/5) + 32. Fuel efficiency is a reciprocal relationship: US mpg and L/100 km cannot be converted by a constant multiplier.

Precision and limitations

Source factors are stored at their defined precision. Display rounding is adjustable, and calculations do not use the displayed rounded output as an intermediate. Floating-point calculations may incur small machine rounding errors. For regulatory, medical, industrial, or safety-critical use, verify values against the applicable authoritative standard.