Stones to Pounds Converter (st to lb and lb to st)

This stones to pounds converter turns stone into pounds and pounds into stone. In the pounds-to-stone direction it gives the answer the way a British or Irish bathroom scale shows it, whole stone plus leftover pounds, as well as decimal stone and kilograms.

The stone is an old British unit that survives mainly for body weight. Its size is fixed: the Weights and Measures Act 1985 defines a stone as 14 pounds, and the pound as exactly 0.45359237 kilograms. That makes a stone exactly 6.35029318 kg. Nothing in the conversion is approximate; the only rounding is in how many decimal places each card shows.

What trips people up is that a stone does not divide into ten. Half a stone is 7 pounds, not 5, and 11.5 stone is 11 st 7 lb, not 11 st 5 lb. The stone and pounds card exists to stop that slip.

1. Type the weight. Decimals are allowed in either direction.
2. Choose Stone to pounds or Pounds to stone.
3. Read the headline. Stone to pounds gives pounds; pounds to stone gives stone and pounds. The cards show pounds, decimal stone, stone and pounds, and kilograms in every case.

To convert a weight that is already in stone and pounds, such as 11 st 6 lb, turn it into pounds first (11 × 14 + 6 = 160) and enter 160 in pounds mode. The presets load 18 stone, 160 lb and 200 lb. Below the converter, one table runs from 1 to 25 stone and another from 100 to 300 lb, each downloadable as CSV.

1. Choose the starting unit. The direction says whether your number is stone or pounds. A negative weight is read as zero.

1. Convert through the kilogram. The pound is stored as exactly 0.45359237 kg and the stone as 14 of those. Converting multiplies by the size of the starting unit and divides by the size of the target, which gives exactly 14 pounds per stone.

1. Split into stone and pounds. The stone total is cut at the decimal point. The whole part is stone; the remainder times 14 is pounds, rounded half up to two places. If those pounds round up to 14, one stone is carried and the pounds read zero, so you never see 9 st 14 lb.

1. Convert to kilograms. The same weight is converted to kilograms through the pound's exact definition.

1. Round for display only. The arithmetic runs at 34 significant digits. Pounds and kilograms are shown to four places, decimal stone to six, and the pound remainder to two, half up with trailing zeros dropped.

The default, 10 stone to pounds:

1. Pounds: 10 × 14 = 140 lb.
2. Stone and pounds: 10 st 0 lb.
3. Kilograms: 140 × 0.45359237 = 63.5029318, shown as 63.5029 kg.

18 stone to pounds: 18 × 14 = 252 lb, or 114.3053 kg.

160 pounds to stone: 160 ÷ 14 = 11.428571 stone. Eleven whole stone are 154 pounds, which leaves 11 st 6 lb. In kilograms that is 72.5748 kg.

11.5 stone to pounds: 11.5 × 14 = 161 lb. Written as stone and pounds that is 11 st 7 lb: the half stone is 7 pounds.

These rows come from the converter's own reference tables, which have more sizes.

There are exactly 14 pounds in a stone. That figure is set in Schedule 1 of the UK Weights and Measures Act 1985, alongside the pound of 0.45359237 kilogram. The two definitions together fix the stone in metric too: 6.35029318 kg, which the kilograms card shows as 6.3503 for one stone.

The stone is not used in the United States, where body weight is given in pounds alone. In the United Kingdom and Ireland, people often quote their weight in stone and pounds even though food and goods are sold in metric units.

• Stone and pounds typed together. There is one input. Convert the stone to pounds yourself (stone × 14 plus the extra pounds) and enter the total in pounds mode.
• Ounces. The pound remainder is shown as a decimal to two places, not as pounds and ounces. For an ounce split, use the kg to lbs converter, which shows both.
• Other stones. Stones of other sizes were once used in particular trades. They are obsolete, and only the 14 lb stone is used here.
• Scale accuracy. The conversion is exact; a bathroom scale reading is not.

• Treating decimal stone as stone and pounds. 11.5 st is 11 st 7 lb, not 11 st 5 lb. Decimal stone counts in fourteenths, not tenths.
• Dividing by 10 for pounds to stone. 160 lb is not 16 stone. Divide by 14 and keep the remainder in pounds: 11 st 6 lb.
• Mixing a stone with a kilogram. A stone is a little over six kilograms, not one. If a weight in stone and a weight in kilograms look similar, one of them is wrong.
• Rounding the remainder away. 14 st 4 lb and 14 st are 4 pounds apart. When you track a change in weight, keep the pounds.

• UK legislation, Weights and Measures Act 1985, Schedule 1, Part V: the stone as 14 pounds and the pound as 0.45359237 kilogram. legislation.gov.uk/ukpga/1985/72/schedule/1
• NIST Handbook 44, Appendix C, General Tables of Units of Measurement: the avoirdupois pound. nist.gov/pml/owm/nist-handbook-44-current-edition
• National Bureau of Standards Miscellaneous Publication 233, Units of Weight and Measure (the 1959 refinement of the yard and the pound, 24 FR 5348). nvlpubs.nist.gov/nistpubs/Legacy/MP/nbsmiscellaneouspub233.pdf