Weight Converter
Convert between all common weight and mass units instantly. Enter a value in any unit — kilograms, pounds, ounces, stone, grams, milligrams, tonnes — and see simultaneous conversion to every other unit. The live grid display shows all values at once with one-click copy. Includes both US (short) and UK (long) tons, plus stone-and-pounds breakdown popular in the UK.
What does this tool do?
The Weight Converter provides real-time conversion between mass units used globally. It supports metric units from milligrams to tonnes, US customary units (ounces, pounds, short tons), and UK-specific units (stone, long tons). The unique stone-and-pounds breakdown shows body weight in the traditional UK format (e.g., 11 st 4 lb). All conversions use the international avoirdupois pound definition. The live grid interface shows your value in every unit simultaneously — edit any field and all others update instantly.
How it works
Conversions use the kilogram as the base unit per the International System of Units (SI). The international avoirdupois pound is defined as exactly 0.45359237 kilograms (defined 1959). Other units derive from this: 1 stone = 14 pounds = 6.35029318 kg; 1 US ton = 2000 pounds = 907.18474 kg; 1 UK ton = 2240 pounds = 1016.0469088 kg. Metric units use powers of 10 from the gram. Precision uses IEEE-754 double precision. The stone-and-pounds calculation divides by 14, with the quotient as stone and remainder as pounds.
Features
- 9+ units displayed: mg, g, kg, tonne, oz, lb, st, US ton, UK ton
- Edit any cell to drive every other
- Stone-and-pounds breakdown for body weight
- Both US (short) and UK (long) tons
- Copy any value with one click
- Adjustable display precision
- Recent conversions saved locally
How to use
- 1
Enter a value
Type in any unit field. Other units update instantly showing equivalent masses.
- 2
Check stone-pounds breakdown
For body weight in stone, the tool shows stone-and-pounds (e.g., '11 st 4 lb') in addition to decimal stone.
- 3
Pick precision
Choose 3, 6, or 9 significant figures depending on whether you need quick estimates or precise measurements.
- 4
Copy needed values
Click any unit value to copy it to clipboard for recipes, shipping labels, medical records, or specifications.
Common use cases
Cooking and recipes
Convert between metric and imperial weight measurements for international recipes and kitchen scales.
Fitness and health tracking
Convert body weight between kg, pounds, and stone for international fitness apps, medical records, and personal tracking.
Shipping and logistics
Calculate shipping weights across different measurement systems for international freight and courier services.
Science and education
Convert between grams, milligrams, kilograms for laboratory work, chemistry calculations, and educational demonstrations.
Tips & best practices
- 1 pound is exactly 0.45359237 kg by international agreement (1959) — all pound-based conversions are exact
- The stone (14 pounds) is still commonly used in UK/Ireland for body weight but rarely for other measurements
- Troy weight (for precious metals) is different from avoirdupois — this tool uses avoirdupois for all conversions
- Metric tonnes (1000 kg) are sometimes called 'metric tons' — distinct from US tons (2000 lb) and UK tons (2240 lb)