A calculation
you can follow.

One base unit, two factors

Length, mass and pressure each use a base unit: metre, kilogram and pascal respectively. To convert a value, first express it in the base unit, then divide by the destination unit’s factor.

For example, converting 12 inches to centimetres:

The reference tables show the factors. They describe international inch and foot definitions, avoirdupois mass units, and conventional pressure units. They do not account for instrument calibration, material expansion or a change in measurement conditions.

Temperature includes an offset

Absolute temperatures use kelvin as the intermediate scale. The conversion first applies the source scale and offset, then reverses the destination scale and offset.

For Celsius, the scale is 1 and the offset is 273.15. For Fahrenheit, the scale is 5/9 and the offset is 273.15 − 32 × 5/9. Kelvin has scale 1 and offset 0.

The calculator rejects temperatures below absolute zero. A tiny negative intermediate value within 10⁻¹⁰ K is treated as zero to accommodate floating-point rounding at the boundary. Temperature intervals require different treatment because their offsets cancel; use the interval explanation in the temperature reference.

Precision is not accuracy

The displayed result uses up to 12 significant digits, with trailing zeroes removed. Small or large values may use scientific notation. This display choice does not add information to the original measurement.

Calculations use JavaScript’s binary floating-point numbers. Many decimal fractions cannot be represented exactly, and intermediate values can carry small rounding errors. Very large values that exceed the numeric range are rejected; extremely small values may underflow to zero.

Caliper does not infer significant figures from the input. A typed value of 1.0 and 1 produces the same numeric result. Round a reported measurement to a precision justified by your instrument, uncertainty and method.

For a quick consistency check, convert the result back into the original unit. Small differences in the last displayed digits can arise from rounding. Avoid repeatedly copying rounded intermediate results into a longer calculation.

Keep the input unambiguous

• Use a full stop as the decimal separator: 12.5.
• Leave out spaces and thousands separators: write 1000, not 1,000.
• Scientific notation is supported: 1e3 means 1,000 and 2.5e-4 means 0.00025.
• Use the unit selectors rather than adding unit symbols to the number.

Changing the quantity loads a small example. The swap button exchanges the selected units and keeps your entered value. No input is submitted to a server or stored by the calculator.