Methodology

This page explains how conversions are calculated and checked so you can judge the results for yourself.

Base units and factors

Each measurement type has one base unit — the meter for length, the kilogram for mass, the kelvin for temperature, and so on. Every other unit stores its exact ratio to that base. To convert, a value is first turned into the base unit and then into the target unit. This two-step method keeps a single source of truth and avoids drift between unit pairs.

Linear and non-linear conversions

Most units are linear: one multiplication converts them. Some are not. Temperature scales have different zero points, so they use explicit formulas with an offset. Fuel economy mixes distance-per-fuel and fuel-per-distance measures, which are reciprocals of one another, so those conversions invert the value where needed.

Distinctions we keep separate

• US and Imperial gallons, fluid ounces, and pints are different sizes.
• Metric tons, US short tons, and UK long tons are treated as distinct units.
• Decimal storage units (KB, MB, GB) use powers of 1000; binary units (KiB, MiB, GiB) use powers of 1024.
• Mass (kilograms) and force (newtons) are different physical quantities.
• Temperature values are treated as absolute readings, not intervals.

Rounding and display

Results are formatted to remove floating-point noise and unnecessary trailing zeros. Very large or very small numbers switch to scientific notation, and you can choose the number of decimal places. The underlying calculation uses full double precision; only the displayed value is rounded.

Verification

An automated test suite checks known reference values (for example, 1 inch = 2.54 cm and 0 °C = 32 °F), confirms that converting a value and converting it back returns the original within a tight tolerance, and covers zero, negative, very large, and very small inputs. Conversions are not published until these tests pass.