Weight Converter

About the Weight Converter

Body weight, baby weight, luggage allowances, postage, recipes, freight and gym weights are all given in different units depending on the country and the context. A British doctor may note weight in kilograms while a patient thinks in stone and pounds; an American recipe asks for ounces while a European one uses grams; a shipping quote comes in tonnes while a supplier quotes tons. Converting between them correctly matters, especially where medicine doses or freight charges depend on the figure.

This weight converter converts between nine units of weight: milligrams, grams, kilograms, tonnes, ounces, pounds, stone, US tons and UK tons. It gives the result, the exact factor both ways, the weight in every other unit, and a practical pounds and ounces and stone and pounds form.

How to Use the Weight Converter

Enter the value to convert.

Choose the unit to convert from and to.

Read the converted weight, the factor, and the weight in pounds and ounces and in stone and pounds for anything over a stone.

How Weight Conversion Works

Every unit has an exact value in kilograms, fixed by the international agreement of 1959:

  1 g       = 0.001 kg             1 oz  = 28.349523125 g   (1/16 lb)
  1 tonne   = 1,000 kg             1 lb  = 0.45359237 kg
  1 US ton  = 2,000 lb             1 st  = 14 lb = 6.35029318 kg
            = 907.18474 kg
  1 UK ton  = 2,240 lb = 1,016.0469088 kg

  result = value × (from-unit in kg) ÷ (to-unit in kg)

Step-by-Step Example: Kilograms to Pounds

70 kg to pounds.

  70 ÷ 0.45359237 = 154.324 lb
  Pounds and ounces:  154 lb + 0.324 × 16 = 154 lb 5.2 oz
  Stone and pounds:   154.324 ÷ 14 = 11 st, remainder 0.3 lb

So 70 kg is about 154.324 lb, 154 lb 5.2 oz, or 11 st 0.3 lb.

Step-by-Step Example: A Baby's Weight

3.5 kg to pounds and ounces.

  To ounces:   3,500 g ÷ 28.349523125 = 123.459 oz
  Pounds:      123.459 ÷ 16 = 7 lb, remainder 11.459 oz

A 3.5 kg baby weighs about 7 lb 11.5 oz, the way birth weights are often announced in the US and UK.

Quick Reference

  1 kg  = 2.20462 lb           1 lb  = 453.592 g
  1 kg  = 35.274 oz            1 oz  = 28.3495 g
  1 kg  = 0.157473 st          1 st  = 6.35029 kg
  1 t   = 2,204.62 lb          1 US ton = 0.907185 t

A simple rough rule is that a kilogram is "two pounds and a bit": double the kilograms and add 10 percent. 70 × 2 = 140, plus 14 is 154, very close to the exact 154.3.

Stone, Pounds and Ounces

The stone of 14 pounds is still the usual unit for body weight in Britain and Ireland, so a person weighing 11 stone 4 pounds weighs 158 pounds, or about 71.7 kilograms. Ounces are divided into 16 per pound, not 10, so a weight such as "7 lb 11.5 oz" cannot be written as 7.115 lb; it is 7.72 lb. Converting to a single unit first avoids those slips.

Tons and Tonnes

Three different tons are in use. The metric tonne is 1,000 kg, the standard for international trade, shipping and science. The US (short) ton is 2,000 pounds, about 907 kg. The UK (long) ton, 2,240 pounds or about 1,016 kg, is now rare but still appears in shipping and historical records. A difference of 10 percent or more between them can matter a great deal on a freight bill or a vehicle's load limit.

Weight and Mass

In physics, the kilogram and pound are units of mass, the amount of matter in an object, while weight is the force of gravity acting on it, measured in newtons. On the Moon, a 70 kg person would still have a mass of 70 kg but would weigh about one sixth as much. On Earth the distinction rarely matters in everyday life, so this converter uses "weight" in its everyday sense.

Precision for Medicines and Science

Medicine doses are often calculated per kilogram of body weight, and a pound-for- kilogram mix-up more than doubles or halves a dose. Health professionals therefore record weight in kilograms and convert with the exact factor rather than a rounded one. In the kitchen, rounding to the nearest gram or quarter ounce is plenty.

Grams and Ounces in the Kitchen

Baking is where precise weights matter most, and it is also where metric and US recipes collide. A US recipe asking for 8 ounces of butter wants about 227 grams; 4 ounces of chocolate is about 113 grams. Many cooks round an ounce to 28 or even 30 grams, which is close enough for most dishes, but over a large batch the rounding adds up. Digital kitchen scales that switch between grams and ounces remove the need to convert at all. Remember that cups and spoons measure volume, so converting them to grams depends on the ingredient: a cup of flour weighs much less than a cup of sugar.

Luggage, Post and Shipping

Airline baggage allowances are usually set in kilograms, often 23 kg for checked bags on international flights, which is about 50.7 pounds — the familiar 50-pound limit on US routes is slightly lower. Postal services price parcels by weight bands, and a few grams over a threshold can move a parcel into a more expensive band, so weigh and convert before you buy postage.

Understanding Your Result

The headline is the converted weight.

The conversion factor shows the exact factor in both directions.

The in every unit line gives the weight in all nine units.

The also line gives pounds and ounces, and stone and pounds for weights of a stone or more.

When Should You Use This Calculator?

Use it to convert body weight between kilograms, pounds and stone.

Use it for baby weights, postage and luggage allowances.

Use it with recipes that use ounces or grams.

Use it for freight, materials and loads quoted in tonnes or tons.

Common Mistakes

Treating ounces as decimals of a pound. 7 lb 11 oz is 7.69 lb, not 7.11 lb.

Confusing tonnes and tons. A US ton is about 9 percent lighter than a tonne.

Rounding the factor to 2.2. Fine for estimates, but 1 percent out on precise work.

Mixing fluid ounces and ounces. Fluid ounces measure volume, not weight.

Forgetting stone is 14 pounds. It is not 10.