Unit converters with explicit measurement conventions
Unit conversion changes the expression of a quantity, not the quantity itself. The main sources of mistakes are choosing the wrong unit family or assuming similarly named units mean the same thing.
Choose by the task
- Check US versus imperial liquid measures, and decimal versus binary storage units.
- Convert temperatures as readings, not temperature intervals. Mass-to-volume needs density and is not a unit-only conversion.
Physical measurements
Length Converter
Convert between millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles.
Weight Converter
Convert common metric and avoirdupois weight units, including kilograms, pounds, ounces, and stone.
Area Converter
Convert metric and US customary area units, including square meters, hectares, acres, and square miles.
Volume Converter
Convert metric volume and clearly labelled US customary liquid-volume units.
Offset and digital units
Linear, squared and offset conversions
Length and mass conversions multiply by a factor. Area requires squared length relationships: a square meter is 10,000 square centimeters, not 100. Temperature readings also include an offset, so doubling 10 °C does not mean twice the physical temperature.
The weight tool converts mass units; it does not compute gravitational force. It also cannot convert a cup of an ingredient into grams without density information. Use volume for capacities, keeping the stated US customary convention in mind.
Read the prefix and preserve useful precision
US gallons and imperial gallons differ. Decimal GB and binary GiB differ. Explicit unit labels are part of the result, not optional decoration. Include them when copying a value into a document.
Displayed decimals may be rounded even when a factor is exactly defined. Avoid converting a rounded output back and forth many times. For tolerances, engineering work or regulated measurements, use the appropriate measurement standard and precision requirements.
Questions about this topic
Can I convert volume directly to weight?
Not with a unit factor alone. You need the material’s density and conditions. The separate volume and mass tools do not assume that every liquid or ingredient has water’s density.