Lbs to kg:
convert American labels, parcels and body weight

How many kilograms are in a pound?

One pound is exactly 0.45359237 kilograms, which is 453.59237 grams. The value was set by the international yard and pound agreement of 1959, so there is nothing to round except your own answer.

Indian shoppers meet pounds more often than they expect: imported baby products, protein tubs, exercise equipment, recipe sites and international courier forms all use them. The label rarely helps you convert.

Grams are more useful than kilograms for small items. A pound is 453.6 g, a tenth of a pound is 45.4 g, and an ounce is 28.35 g, which is how recipes and cosmetics are labelled.

As a rule of thumb, a kilogram is about 2.2 pounds and a pound is a little under half a kilogram. For a rough answer, halve the pounds and then take off a tenth of that half.

This article deals with weights that begin in pounds: American product labels, parcels, baby scales and the stones and pounds still used in Britain. If you are working from a kilogram figure, such as a luggage limit, read the kg to lbs article.

Lbs to kg formula, including ounces

1. 1Divide the ounces by 16 to get a fraction of a pound.
2. 2Add that to the whole pounds.
3. 3Multiply the total by 0.45359237.
4. 4Round to the precision you need, such as two decimals for kilograms or the nearest gram.

Half a pound is 226.8 g and a quarter of a pound is 113.4 g, which is about the weight of a 4 oz burger patty. Those two figures cover most small package weights you will see.

Accuracy matters more as the weight grows. For 200 lb, dividing by 2.2 gives 90.91 kg, while the exact figure is 90.72 kg, a gap of 0.19 kg. Use 0.45359237 whenever the result goes into a form.

If you prefer, convert ounces on their own: one ounce is 0.0283495 kg, or about 28.35 g. The two routes give the same answer.

Worked example: a baby weighing 7 lb 8 oz

A newborn's weight on an American discharge sheet reads 7 lb 8 oz, and the family wants it in kilograms.

A second reading works the same way: 6 lb 13 oz is 6 + 13 ÷ 16 = 6.8125 lb, which is 3.09 kg.

Do not read 7.8 for 7 lb 8 oz: the 8 is ounces, not tenths of a pound. It is an easy slip when translating a discharge sheet. For anything about a baby's growth, rely on the doctor's charts.

Pounds to kilograms for everyday items

Smaller food and cosmetic packs use ounces. 8 oz is 227 g, 12 oz is 340 g and 16 oz, a full pound, is 454 g.

Combine rows when a weight is not listed. For 35 lb, add the 25 lb row (11.34 kg) and the 10 lb row (4.54 kg) to get 15.88 kg, which matches 35 × 0.45359 = 15.88 kg.

Most conversions you will make are between 1 and 50 lb, where one decimal place of a kilogram is accurate enough. Round to the nearest half kilogram when you quote freight, since carriers rarely work to the gram.

Pay attention to the 45 lb row. A standard American plate is not 20 kg: it is 20.41 kg, which adds about 0.4 kg per plate and about 0.8 kg per pair.

Recipes, parcels and shipping weight

Shipping weight on a US product page is often given in pounds, to one decimal. A 2.5 lb item is 1.13 kg, and an 8.2 lb item is 3.72 kg.

Recipes work the same way. Two pounds of chicken is 907 g, a pound of butter is 454 g and a 4 oz stick of butter is 113 g. A scale set to grams is easier than measuring cups, and you avoid rounding.

Heavier purchases follow the same method. A pair of 35 lb dumbbells is 70 lb, or 31.75 kg, before packaging. Convert the total, not each item, and then add the box weight.

Many couriers bill in steps of a fixed amount, so convert, then round up to the next step. Packaging adds weight too, so build in a margin of at least 10% before you compare against a slab limit.

Stones and pounds in UK body weight

Britain still describes body weight in stones, where 1 stone is 14 lb or 6.35 kg. Someone who weighs 11 st 4 lb has a weight of 11 × 14 + 4 = 158 lb, or 158 × 0.45359237 = 71.67 kg.

Another example: 9 st 7 lb is 9 × 14 + 7 = 133 lb, which is 133 × 0.45359237 = 60.33 kg. Convert to pounds first, then to kilograms, and the stones never cause trouble.

Stones are not decimals either. A weight of 11 st 4 lb is not 11.4 stone, and doing it that way overstates the weight by about 1.6 lb, because 11.4 stone is 159.6 lb.

Mistakes with lbs to kg

• Reading 7 lb 8 oz as 7.8 lb instead of 7.5 lb. Ounces are sixteenths, not tenths.
• Dividing by 2.2 and treating the result as exact. 150 ÷ 2.2 = 68.18 kg, while the true figure is 68.04 kg.
• Using 0.5 as the factor for body weight. It overstates kilograms by about 10%, so 150 lb would become 75 kg instead of 68.04 kg.
• Mixing mass and force. A pound is a unit of mass here, and lbf is a different unit for force.
• Forgetting that a US 'ton' and a metric tonne differ. A short ton is 2,000 lb (907.18 kg), while a tonne is 1,000 kg.
• Rounding each item before adding. Total the pounds first, convert once, and round the final figure.

When an exact figure matters, such as a prescription, ask the professional rather than relying on a converted number, and quote the original unit alongside it.