2 Stones to Pounds

Two stone is 28 pounds, 12.70058636 kilograms and 448 ounces

Two stone is 28 pounds. That is the whole definition, and every other number follows from it. In kilograms, 28 x 0.45359237 = 12.70058636 kg, using the exact pound that NIST Special Publication 811, Appendix B.8 prints as 4.535 924 E-01 kg. In ounces, 28 x 16 = 448 oz, and in grams it is 12700.58636 g.

British law still carries the number. Schedule 1 of the Weights and Measures Act 1985 lists Stone = 14 pounds, Quarter = 28 pounds, Hundredweight = 112 pounds and Ton = 2240 pounds, with the pound set at 0.453 592 37 kilogram. Those lines sit in Part VI, the list of units that may not be used for trade except as supplementary indications. That is why a British shop sells potatoes in kilos and a British bathroom scale still reports stones.

The unit is a package of 14 pounds, the way a dozen is a package of 12. Two of those packages make 28 pounds, four make 56 pounds, and eight make 112 pounds, which is one hundredweight. The table below covers the small stone counts that come up at a doctor's office, a gym or a race card.

Why two stone is also one quarter, and where the law names both

The old British trade table did not stop at the stone. It also had the quarter at 28 pounds, the hundredweight at 112 pounds and the ton at 2240 pounds. Two stone and one quarter are the same weight, written for two different trades. A farmer selling grain might say a quarter, while a person checking a bathroom scale says two stone.

Those units are now supplementary. Part VI of the 1985 Act says they may not be used for trade except as additional information, so a market stall must price in kilograms or grams and may print pounds and ounces beside that. The stone survives because body weight is not a retail transaction. NHS scales, gym scales and race cards keep it, and British people keep reading it.

Ireland uses the stone the same way, and a Irish scale often shows both stone and kilograms. The United States does not. A US product label, a US doctor's chart and a US gym scale all use pounds, so a reader in Ohio who meets "2 st" in a British article needs the 28 lb version before anything else makes sense.

This is also why a British person might say they lost "two stone" and an American hears nothing concrete. The British statement is 28 pounds, or 12.70058636 kg. The American statement of the same loss is 28 pounds. Same mass, different packaging, and the package is the only thing that changes.

Reading 2 st on a British scale and a US scale

A British mechanical scale marks whole stones and then 14 pound ticks. Two stone is the second mark, and the needle sits on zero pounds if the weight is exact. If the needle sits five ticks past the two, the weight is 2 st 5 lb. That is 2 x 14 + 5 = 33 pounds, and 33 x 0.45359237 = 14.96854821 kg.

Seven ticks past the two is 2 st 7 lb, or 35 pounds. In kilograms that is 35 x 0.45359237 = 15.87573295 kg. A scale that only marks half stones will call both 2 st 5 lb and 2 st 7 lb "two and a half stone", which is why the printed number and the spoken number often differ by a pound or two.

A digital scale set to kilograms shows 12.7 for two stone, because the display rounds 12.70058636 to one decimal place. A digital scale set to pounds shows 28.0. Neither is wrong. The kilogram display has thrown away 0.00058636 kg, which is 0.58636 g, and no bathroom scale can resolve that.

The half stone is the smallest step most British scales mark. Half a stone is 7 pounds or 3.17514659 kg. Quarter stone marks are rarer, and they stand for 3.5 pounds or 1.587573295 kg. When a British article says "two and a half stone", it means 35 pounds, not 28.

What 28 pounds looks like in kilos, pounds and ounces

The table below runs from half a stone to five stone, so you can read a weight range without doing the multiplication each time. The two stone line is the one this page is about, but the neighbours matter when a scale lands between marks.

Two stone is 12.70058636 kg, but most people will say 12.7 kg. That shortcut is fine for a suitcase and fine for a gym plate. It is not fine when you add up several conversions, because each 12.7 carries a 0.58636 g shortfall. Ten such conversions lose 5.8636 g, which is still small, but a hundred lose 58.636 g, about two ounces.

In ounces, two stone is 448 oz. A 28 oz bag of coffee is 1.75 lb, so 28 lb is 16 of those bags. A 16 oz box of pasta is 1 lb, so 28 lb is 28 boxes. Those comparisons are easier to feel than a decimal kilogram.

A two stone drop: weeks, BMI points and daily pace

A two stone goal is 28 pounds or 12.70058636 kg. At 1 pound per week, 28 / 1 = 28 weeks. At 2 pounds per week, 28 / 2 = 14 weeks. In metric, at 0.5 kg per week, 12.70058636 / 0.5 = 25.4 weeks. Those are arithmetic, not a plan, and a doctor should set the pace for any weight change that matters.

Body mass index moves with the square of height, so the same 28 pounds is worth more BMI points on a short frame. The formula is 703 x pounds / inches squared. At 5 ft 4 in (64 in), 703 x 28 / 4096 = 4.81 BMI points. At 5 ft 9 in (69 in), 703 x 28 / 4761 = 4.13 points. At 5 ft 10 in (70 in), 703 x 28 / 4900 = 4.02 points. At 6 ft (72 in), the same drop is 3.80 points.

Those numbers explain why two people lose the same 28 pounds and see different results on a chart. The scale moves the same amount. The chart moves more for the shorter person. Neither result says anything about health on its own, and BMI is a rough population measure, not a diagnosis.

If you weigh yourself daily, a two stone drop is 28 lb of scale movement. Water weight can swing 2 to 4 lb in a day, so the trend line matters more than any single morning. A 28 lb change measured over 14 weeks is 2 lb per week on average, and a single 3 lb jump on a Tuesday does not break that average.

The table turns that formula into a quick reference. Each row holds the height fixed and applies the same 28 pound drop, so the only thing changing is inches squared.

Two stone in sport, travel and shipping

Boxing in Britain quotes limits in stones. A light heavyweight at 12 st 7 lb weighs 12 x 14 + 7 = 175 pounds, or 79.37866475 kg. A heavyweight at 14 st 7 lb weighs 203 pounds, or 92.07925111 kg. The gap between those two fighters is 2 st exactly, which is 28 pounds, or 12.70058636 kg. A US broadcast would call the same gap 28 pounds and skip the stone entirely.

Horse racing still prints weights in stones and pounds. A handicap entry of 9 st 2 lb is 9 x 14 + 2 = 128 pounds, or 58.05982336 kg. An entry at 11 st 2 lb is 156 pounds, or 70.76040972 kg. Two stone of handicap weight is the difference between those two cards, and it is a large spread in a race.

Airline luggage is metric almost everywhere. A 23 kg limit is 23 / 0.45359237 = 50.7063203 pounds, or 3 st 8.7 lb. Two stone is 12.70058636 kg, which is 55.2 percent of that limit. A 20 kg limit is 44.0924466 pounds, and two stone is 63.5 percent of it. If your bag weighs 28 lb, you have 22.7 lb of room under a 23 kg cap.

At the gym, two 14 lb dumbbells are 28 lb together, which is 2 st. A 20 kg plate is 44.0924466 lb, or 3 st 2.1 lb. A 45 lb barbell is 3 st 3 lb, or 20.41165665 kg. Those are the numbers to check before you add a plate and wonder why the bar feels heavier than the label.

Rounding 28 pounds to 12.7 kilos: where the digits go

The kilogram is the SI base unit of mass, and the BIPM SI Brochure is where its current definition lives. The exact answer here is 12.70058636 kg. Written as 12.7 kg, it is 0.00058636 kg light, which is 0.58636 g. That is less than a raisin, and no kitchen or bathroom scale will notice. The rounding only matters when you multiply it across many items or when you reverse it and expect the original pounds to come back.

Reverse the shortcut and 12.7 / 0.45359237 = 27.9987073 pounds. That is 0.0012927 lb under 28, or 0.58636 g. The missing gram is the same one, wearing a different unit. If you type 12.7 kg into a converter and get 27.9987 lb, the converter is right and the input was rounded.

Scale resolution sets a floor on the argument. A scale that reads to 0.1 kg jumps in 0.220462 lb steps. A scale that reads to 0.2 lb jumps in 90.718474 g steps. Two scales can disagree by one step and both be within their stated tolerance. For a two stone check, that is 0.2 lb out of 28, or 0.7 percent.

The clean way to write the result is "2 st 0 lb" for a British reader and "28 lb 0 oz" for a US reader. In metric, write 12.70058636 kg if the number is a definition, and 12.7 kg if it is a scale reading. Mixing the two styles is how a page ends up claiming that 2 st is 12.7 kg exactly, which it is not.