1 Stone to Pounds

One stone is 14 pounds, 6.35029318 kilograms and 224 ounces

One stone is 14 pounds. That is the whole definition, and every other number follows from it. In kilograms, 14 x 0.45359237 = 6.35029318 kg, using the exact pound that NIST Special Publication 811, Appendix B.8 prints as 4.535 923 7 E-01 kg. In ounces, 14 x 16 = 224 oz. Nothing about the stone is metric, so a British scale and a European scale never show the same digits for the same body.

British law still carries that number. Schedule 1 of the Weights and Measures Act 1985 lists Stone = 14 pounds, Quarter = 28 pounds, Hundredweight = 112 pounds and Ton = 2,240 pounds, with the pound set at 0.453 592 37 kilogram. Those lines sit in Part VI of the schedule, the list of units that may not be used for trade except as supplementary indications, which is why a British shop sells potatoes in kilos and a British bathroom scale still reports stones.

The unit is a package deal of 14 pounds, the way a dozen is a package of 12. You cannot buy 1.3 stone of anything in a shop, and nobody says 0.6 stone. A weight lands either on a whole stone or between two of them, written as a pair such as 10 st 5 lb.

Once you know that 1 stone is 14 pounds, every larger figure is a multiplication. Two stone is 28 pounds, five stone is 70 pounds, and ten stone is 140 pounds. The table below covers the first ten stones in all three units, which handles most body weights and most gym loads.

Stones in the ring, at the track and on the gym floor

British horse racing still states weights in stones and pounds. A handicap entry of 9 st 2 lb is 9 x 14 + 2 = 128 pounds, which is 128 x 0.45359237 = 58.05982336 kg. The same horse at 8 st 10 lb carries 122 pounds. Stewards read the gap between two entries in pounds, but the race card prints stones because the rule book is written that way.

Boxing in Britain quotes a heavyweight at 15 st or 16 st where a US broadcast says 210 or 224 pounds. Fifteen stone is 210 pounds and 95.2543977 kg, which puts a fighter just over the 200 pound cruiserweight limit that most sanctioning bodies use. A 16 st heavyweight is 224 pounds, the same number as the ounces in a stone, which is a coincidence worth remembering and nothing more.

The gym is where the two systems collide. A 20 kg plate is 44.0924466 pounds, or 3 st 2.1 lb, and a 45 pound plate is 20.41165665 kg. Load a 20 kg bar with two 20 kg plates and the total is 60 kg, which is 132.2773573 pounds or 9 st 6.3 lb. Swap those plates for a pair of 45s and the same bar reads 134.0924466 pounds, or 9 st 8.1 lb.

Race weights, ring weights and plate weights all come back to the same 14. None of them is a bathroom measurement, and that is the point: the stone turns up wherever a British form was printed before metrication, from a race card to a gym chalk board.

What one stone feels like: objects that weigh about 14 pounds

Fourteen pounds is a weight most adults have lifted without thinking about it. A league bowling ball at 14 pounds is the closest match, and it is a single object you can pick up with one hand, which makes it a good mental anchor for the unit.

A 14 pound bag of dog food is the same weight, and so is a fully packed carry-on that stays under the cheap-fare limits. A six month old baby is usually around 16 pounds, a little over a stone, and a case of 24 half liter water bottles is about 26.5 pounds of water before the cardboard, close to two stone.

Metric readers can use the same trick in reverse. One stone is 6.35 kg, which is roughly a 6 liter bottle of water plus a mug. Two stone is 12.7 kg, about a full 12 kg suitcase. The table lines up several everyday loads so you can check a claim like "I lost a stone" against something you have lugged to the car.

One stone seven: writing weight the British way

British body weight comes as two numbers, and the second one is where most conversions go wrong. Read 1 st 7 lb as one stone plus seven pounds, which is 14 + 7 = 21 pounds. Multiply 21 by 0.45359237 and you get 9.52543977 kg. Read it as 1.7 stone and you land on 23.8 pounds, which is nearly three pounds heavy.

The pound part runs from 0 to 13 and then rolls over. At 1 st 13 lb the weight is 27 pounds or 12.24699399 kg, and one more pound makes it 2 st 0 lb. That rollover is why a British scale never shows 1 st 14 lb, and why a recipe or a form that asks for stones needs both boxes filled.

Going the other way, divide the pounds by 14 and keep the remainder. Take 145 pounds: 145 / 14 = 10.357, so the whole part is 10 stone, and 145 - 140 = 5 pounds left over. The answer is 10 st 5 lb, which is 65.77089365 kg. That is the same arithmetic a nurse does when a US chart meets a UK patient.

A stone on a metric scale, and the half stone step

A scale bought in Europe shows kilograms, and one stone on that display is 6.4 kg after rounding to one decimal. The exact figure is 6.35029318 kg, so the display is 0.0497 kg high, about 50 g. That is smaller than the difference between two weighings of the same body, so ignore it.

The error grows when you multiply. Five stone is 31.7514659 kg, and five times a rounded 6.4 is 32.0 kg, which is 0.2485 kg heavy. On a hospital form that quarter kilo is noise. On a shipping label for a 5 stone parcel it can decide which price band you pay.

Half a stone is 7 pounds, or 3.17514659 kg, and it is the marked step on most British bathroom scales, so a coach who asks for half a stone a week is asking for 3.2 kg. A quarter stone is 3.5 pounds or 1.587573295 kg, and one tenth of a stone is 1.4 pounds or 0.635029318 kg. Write the unit next to any target, because 3 kg and 3 lb are not the same instruction.

For a quick mental check, one stone is a little over 6.3 kg, and 6 kg is 13.23 pounds, a little under a stone. If a metric scale reads 6.3 kg and a British scale reads 1 st 0 lb, they are describing the same weight with different rounding.

One stone in luggage, parcels and gym plates

Airline limits are written in kilos or pounds, never in stones, so a stone is a useful way to divide a limit into pieces. A 23 kg checked bag allowance is 23 / 0.45359237 = 50.7063203 pounds, which is 3 st 8.7 lb. One stone is 14 of those 50.7 pounds, so a third of the allowance is a bit under 1 st 3 lb.

A 50 pound bag limit on a US domestic flight is 3 st 8 lb exactly, since 50 / 14 = 3.571. A 20 kg parcel is 44.0924466 pounds, or 3 st 2.1 lb. A 7 kg cabin bag is 15.4323584 pounds, which just edges past one stone by 1.43 pounds.

Gym plates use the same split. A 45 pound plate is 3.21 stone and 20.41165665 kg, while a 20 kg plate is 44.09 pounds, or 3 st 2.1 lb. A standard 45 pound Olympic bar is 3 st 3 lb, and a bar loaded with two 45s a side is 225 pounds, which is 16 st 1 lb and the bench mark lifters call two plates.

A one stone goal in pounds, kilos and weeks

Weight goals in Britain are usually stated in stones, which hides the size of the ask. One stone is 14 pounds, and at a steady 1 pound a week that is 14 weeks. At 2 pounds a week it is 7 weeks. Half a stone is 7 pounds, so the same pace gives 7 weeks or 3.5 weeks.

Put the loss against the starting weight and the number looks different again. Losing a stone from 200 pounds is 14 / 200 = 7 percent. Losing it from 140 pounds is 10 percent, which is the first milestone many programs use. In metric, a stone off a 90 kg body is 6.35029318 / 90 = 7.1 percent.

If the goal is written as a target weight, subtract first and convert second. From 12 st 4 lb (172 pounds) to 11 st 0 lb (154 pounds) the gap is 18 pounds, which is 1 st 4 lb or 8.16466266 kg. From 11 st to 10 st the gap is 14 pounds or 6.35029318 kg, and at 1 pound a week that is one season of Saturdays.

These are arithmetic, not a plan. A clinician can say whether a goal fits your health, and a scale reading at home moves by a pound or two either way depending on salt, water and the time of day. Track the weekly average rather than a single morning.