Weight and Mass Converter

Unit conversion expresses the same physical quantity in a different unit of measure. A length stays the length it was; only the number and the label change, because each unit is defined as a fixed multiple of the same underlying quantity.

Every value here is converted through a base unit: the input is multiplied by its factor to reach the base, then divided by the target factor. Two steps, so a category with fifteen units needs fifteen numbers rather than two hundred pairs.

• Pick a category first. The unit lists and the reference table below both follow the category you select.
• Type into either field. Both are editable, so the conversion runs in whichever direction you are working, and it updates live with no button to press.
• Use Swap to turn the conversion around. The values move with their units, so the equation on screen stays true.
• Copy puts the plain result on the clipboard, without a thousands separator, so it can be pasted straight into a spreadsheet or a shell.
• The line under the fields repeats the conversion with both units named, so it is clear which way it ran.

Temperature scales have different zero points, so a single factor cannot express them. Celsius, Fahrenheit, Kelvin and Rankine are converted through Celsius with an offset as well as a ratio, which is why 0 °C is 32 °F rather than 0 °F.

• A kibibyte is 1024 bytes, a kilobyte is 1000. Both are offered, because storage vendors and operating systems disagree about which one they mean.
• Data rates are based on bits, storage on bytes. That factor of eight is why a 1 Gbps line downloads at about 125 MB/s.

Results carry up to fifteen significant digits, the most a double holds reliably, so exact definitions come through whole: 1 mile is 1609.344 m. From a quadrillion up and below a millionth they switch to exponent notation, such as 1e-9. Calculations use double-precision floating point, so a conversion chained through several units can drift in the last digits.