Convert a mass measurement
- Enter a nonnegative decimal mass and its source unit.
- Select the target unit, taking care to choose the correct kind of ton.
- Convert, review the kilogram equivalent and multiplier, then copy or download.
Mass, pounds and tons
In everyday usage these are called weight units; this tool converts mass. It does not calculate gravitational force in newtons or pound-force. One avoirdupois pound is 0.45359237 kilograms and contains 16 avoirdupois ounces. One stone is 14 pounds, consistent with the Unicode unit definitions. Enter decimal stones or use separate whole-stone and pound fields: 10.5 stones means 10 stones 7 pounds. Pounds-and-ounces entry uses whole pounds plus fewer than 16 ounces.
A metric tonne is 1000 kg. A US short ton is 2000 pounds (907.18474 kg), while an Imperial long ton is 2240 pounds (1016.0469088 kg). The selectors keep these definitions separate. Ounces here are avoirdupois mass ounces; fluid ounces measure volume and troy ounces use another mass definition.
Calculation: value × source kilogram factor ÷ target kilogram factor. Factors follow NIST’s unit tables. Definitions are exact; browser arithmetic has finite precision.
| Unit | Kilograms per unit |
|---|---|
| Micrograms (µg) | 1e-9 |
| Milligrams (mg) | 0.000001 |
| Grams (g) | 0.001 |
| Kilograms (kg) | 1 |
| Metric tonnes (t) | 1000 |
| Avoirdupois ounces (oz) | 0.028349523125 |
| Avoirdupois pounds (lb) | 0.45359237 |
| Stones (st, 14 lb) | 6.35029318 |
| US short tons (2000 lb) | 907.18474 |
| Imperial long tons (2240 lb) | 1016.0469088 |
Limits and privacy
Nonnegative source values up to 10¹⁵. Underflow is rejected. No troy/apothecaries units, fluid-volume conversion, density calculation or force conversion. Results display up to 12 significant digits and six decimal places or scientific notation for extremes. CSV retains the JavaScript numeric result with possible floating-point rounding.
Measurements stay in browser memory, with no requests, uploads or saved values. Live conversion waits 300 ms after editing. Swap keeps the numeric value; Use result as next input swaps direction and uses the unrounded result. Swap, examples, Reset and result reuse offer one undo step; typing discards it. Reset clears results and restores one pound to kilograms. The comparison table and all-units CSV cover every supported unit for the same mass; an empty exported value denotes a numeric precision limit.
Can I convert a fluid ounce to grams?
Not with a mass-unit ratio alone. A fluid ounce is volume, and the substance’s density is needed to calculate mass.