Weight Converter Guide: Kilograms, Pounds, Ounces, and Stones

Weight conversions come up when a recipe is written in ounces, a bathroom scale reports stones, a shipping quote wants kilograms, and a gym plate is stamped in pounds. The core factor is short: one kilogram is 2.20462 pounds. Everything else builds from there.

The Factors Worth Knowing

• 1 kg = 2.20462 lb; 1 lb = 0.453592 kg
• 1 lb = 16 oz; 1 oz = 28.3495 g
• 1 stone = 14 lb = 6.35 kg
• 1 metric tonne = 1,000 kg = 2,204.6 lb
• 1 US short ton = 2,000 lb = 907.2 kg; 1 UK long ton = 2,240 lb = 1,016 kg

For mental arithmetic, doubling and adding 10% converts kg to lb closely: 70 kg becomes 140 plus 14 = 154 lb, against a true 154.3. Going the other way, halve and subtract 10%: 180 lb becomes 90 minus 9 = 81 kg, against a true 81.6.

Worked Conversions

A person weighing 82 kg is 180.8 lb, which is 12 stone 12.8 lb. A 5 lb bag of flour is 2.27 kg. A recipe calling for 8 oz of butter needs 227 g. A 500 g pack of pasta is 17.6 oz, slightly over a pound. A shipment of 3.5 short tons is 3,175 kg, or 3.18 tonnes.

Stones and Pounds

British and Irish body weight is still commonly given in stones and pounds, where each stone is 14 pounds. To convert 11 stone 6 lb to kilograms, first make it pounds: 11 x 14 + 6 = 160 lb, then multiply by 0.4536 to get 72.6 kg. Going the other way, 68 kg is 149.9 lb, which is 10 stone 9.9 lb, since 10 x 14 = 140 with 9.9 left over. Decimal stones are almost never used in speech, so always express the remainder in pounds.

Mass Versus Weight

Strictly, mass is the amount of matter and weight is the force gravity exerts on it, measured in newtons. A 70 kg person has a weight of about 687 newtons on Earth and about 114 on the Moon, while their mass is 70 kg in both places. Everyday language uses weight for mass, and scales are calibrated for Earth gravity, so the distinction only matters in physics problems and in engineering where forces are being summed.

Troy Ounces Are Different

Precious metals use troy weight, where one troy ounce is 31.103 g rather than the 28.35 g of an avoirdupois ounce, about 10% heavier. A troy pound has only 12 troy ounces and weighs 373 g, less than a normal pound. Quoting a gold price per ounce without specifying troy introduces a 10% error, which on bullion is a lot of money. Carat, used for gemstones, is different again at exactly 200 mg, and should not be confused with karat, which describes gold purity out of 24.

Cooking by Weight

Weighing is more reliable than volume for dry ingredients, because packing changes volume but not mass. Useful equivalents: 1 cup of plain flour is about 120 g, granulated sugar 200 g, brown sugar packed 220 g, butter 227 g, and rolled oats 90 g. Note how different those are for the same cup, which is exactly why professional baking recipes are written in grams. Bakers percentages take this further, expressing every ingredient as a percentage of flour weight, so a recipe scales to any batch size without conversion errors.

Shipping and Freight Weight

Carriers charge on the greater of actual weight and volumetric weight, which converts parcel size into a billed weight. A common divisor is 5,000 cubic centimetres per kilogram, so a box of 40 by 30 by 20 cm has a volumetric weight of 24,000 / 5,000 = 4.8 kg. Ship a 2 kg pillow in that box and you pay for 4.8 kg. Knowing this before packing often saves more than any negotiated rate.

Reference Points

Errors to Watch

Using 2.2 instead of 2.20462 is fine for body weight and wrong for a 20-tonne load, where it drifts by about 40 kg. Mixing short tons, long tons, and tonnes in the same document is a classic freight mistake. And treating fluid ounces as ounces of weight only works for water; 8 fl oz of oil weighs about 7.4 oz.

Convert Weights Free

The weight converter on SimpleCounter handles grams, kilograms, tonnes, ounces, pounds, stones, and both tons, including stones-and-pounds output for body weight. It is free, runs in your browser, and works on a phone in the kitchen or at the post office.