Weight Converter: Units, Formulas, and Examples
Convert mass between kilograms, pounds, grams, ounces, stones, and clearly defined tons.
How to convert weight
Converted value = input value × source factor ÷ target factor. Factors express each unit in kilograms.
Keep the source and target definitions consistent, apply the conversion to the original value, and round the final answer to the precision needed for your calculation.
Understanding weight units
In everyday language these are called weight units, but kilograms and pounds here measure mass. One avoirdupois pound equals exactly 0.45359237 kilograms. A troy ounce differs from an everyday avoirdupois ounce.
| Unit | In kg |
|---|---|
| Kilograms (kg) | 1 |
| Grams (g) | 0.001 |
| Milligrams (mg) | 0.000001 |
| Micrograms (µg) | 0.000000001 |
| Metric tonnes (t) | 1,000 |
| Pounds (avoirdupois) (lb) | 0.45359237 |
| Ounces (avoirdupois) (oz) | 0.028349523125 |
| Stones (st) | 6.35029318 |
| US short tons (US ton) | 907.18474 |
| Imperial long tons (Imp ton) | 1,016.0469088 |
| Troy ounces (ozt) | 0.0311034768 |
Worked weight examples
1 kilogram is approximately 2.2046226218 pounds. 1 stone = 14 pounds. 1 metric tonne = 1,000 kilograms.
Frequently asked questions
Which definitions should I use?
A US short ton is 2,000 pounds; an Imperial long ton is 2,240 pounds. Neither equals a metric tonne. Force units such as newtons require gravitational acceleration and are not mass conversions.
Why do displayed results sometimes differ slightly?
Intermediate arithmetic uses browser floating-point numbers. Display rounding and the precision of an original measurement can affect the last digits. The unit conversion does not improve the accuracy of a measured value.
Does converting back recover the original value?
Using the unrounded result normally recovers the original quantity within floating-point precision. Copying a rounded number can introduce a small difference.
How are the unit definitions documented?
For physical unit definitions and conversion factors, see the NIST conversion reference.