Recipes from another country, a suitcase allowance in kilograms, a doctor's scale in stone, a parcel rate in pounds: weight conversions come up constantly and the mental shortcuts are rarely precise enough. This converter handles ten units of mass, from the milligram to the long ton, and shows the answer as soon as you type a number.
Every result is also listed in all the other units at once, which is handy when a form asks for pounds but you also want to see stone or grams. The calculation happens in your browser using exact definitions, so the numbers you see are not approximations borrowed from a lookup chart.
Pounds, kilograms and the other units
The kilogram is the base unit of mass in the metric system. The pound used in the US, the UK and most other places is the avoirdupois pound, which has been defined since 1959 as exactly 0.45359237 kg. The ounce is one sixteenth of that, exactly 28.349523125 g, and the stone, still common for body weight in Britain and Ireland, is 14 pounds or 6.35029318 kg.
Heavier loads use tons, and the word means three different things. A metric ton (tonne) is 1,000 kg. A US ton, also called a short ton, is 2,000 lb or 907.18474 kg. A long ton, the old British ton, is 2,240 lb or 1,016.0469088 kg. The carat used for gemstones is a metric unit of exactly 0.2 g; it is not the same as the karat that describes gold purity.
Strictly speaking these are units of mass, not weight, which is a force. In everyday language and on every kitchen and bathroom scale the two words mean the same thing, and this tool follows that convention.
Typical reasons to convert weight
Luggage and shipping limits
Many airlines set a checked-bag limit of 23 kg, which is 50.7063203025 lb, so a bag that reads 51 lb on a home scale is already slightly over. Couriers that price by the pound or kilogram can be compared the same way.
Cooking and baking
American recipes measure in ounces and pounds, European ones in grams. One pound is exactly 453.59237 g and 100 g is about 3.53 oz. For baking, where precision matters, convert the weight once and round sensibly rather than relying on cup measures.
Body weight and fitness tracking
A reading of 11 stone equals 154 lb or 69.85322498 kg. If your gym logs plates in pounds but your scale shows kilograms, keeping both in view avoids confusion when tracking progress.
Jewellery and gemstones
Stones are weighed in carats, and since one carat is 0.2 g, a 1.5 ct diamond weighs 0.3 g. Converting to milligrams can help when comparing lab reports.
How the converter calculates
Each unit is stored as its exact equivalent in kilograms. When you enter a value, the tool multiplies it into kilograms and divides by the target unit, then trims floating-point noise and shows up to 12 significant digits. That is why 1 kg reads 2.20462262185 lb and 70 kg reads 154.323583529 lb, while conversions that are exact, like 1 lb to 453.59237 g, show every digit.
The From and To menus choose the direction, the swap button reverses it, and the All units table underneath gives the same mass in milligrams, grams, kilograms, metric tons, carats, ounces, pounds, stone, US tons and long tons. A short note below the result repeats the key definitions so you can check which ton you are looking at.
Come usare questo strumento
- Enter the amount in the Value field, for instance 23.
- Set From to the unit on your label or scale, such as Kilogram (kg).
- Set To to the unit you need, such as Pound (lb); the result updates as you type.
- Copy the result, or pick another unit from the All units table to switch the target.
Limitations
- Troy ounces and troy pounds, used for gold and silver, are not included. A troy ounce is about 31.1 g, heavier than the 28.35 g avoirdupois ounce shown here.
- Stone and pounds cannot be entered together. For 10 st 6 lb, convert 146 lb, or enter 10.4286 st.
- A comma before exactly three digits is a thousands separator (2,000 is two thousand); any other lone comma, as in 2,5, is a decimal separator.
- The tool converts units only. It does not adjust for gravity, buoyancy or the density of an ingredient, so it cannot turn grams of flour into cups.