Stones to Kilograms Converter

One stone equals about 6.35 kg, or 6.35029318 kg to be exact. The derivation: 1 stone is fixed at 14 pounds (UK 1835 Weights and Measures Act), and 1 pound is fixed at 0.45359237 kg (1959 international yard and pound agreement). Multiply 14 x 0.45359237 = 6.35029318 kg. For mental math, treat a stone as 6.35 kg. So 10 stone is 63.5 kg, 11 stone is 69.85 kg, and 12 stone is 76.2 kg.

Tradition and habit, not legal requirement. The stone has been the everyday unit for personal body weight in the UK and Ireland since merchants standardized it for wool, cheese, and meat trading in medieval markets. Modern UK life uses metric for most things (groceries are sold in grams, fuel in liters, distances on road signs in miles being the visible exception), but bathroom scales, gym kit, and casual conversation about weight stayed in stones. NHS clinical records and prescription dosing usually use kilograms, but a GP will happily tell you that you weigh 11 stone 4 pound rather than 71.7 kg, because that is how the patient thinks of their weight.

Because the kilogram is the SI base unit for mass, and SI is the official measurement system in nearly every country outside the United States, Liberia, and Myanmar. Science, medicine, international trade, manufacturing, shipping, and food packaging are kg-first. Even the US uses kilograms in scientific work, medical drug dosing, and Olympic sports. The kilogram has been redefined (most recently in 2019) in terms of fundamental physical constants like Planck's constant, which makes it reproducible in any well-equipped lab without reference to a physical artifact. Stones, by contrast, are used for body weight only in two countries and are not legal for trade anywhere.

Stone-and-pound notation lists the whole stones first, then the leftover pounds (always under 14). 10 stone 7 pound means 10 x 14 + 7 = 147 pounds, which works out to 66.7 kg. The converter accepts that combined form directly under the "Stones and pounds" input mode: enter 10 in the stones field and 7 in the pounds field. You can also enter the same weight as 10.5 stone (in decimal stones mode), 147 lb, or 66.7 kg and see all four forms simultaneously.

Most adults fall between 10 stone (63.5 kg / 140 lb) and 17 stone (108 kg / 238 lb), depending on height, sex, build, and body composition. The middle of the band, around 11 to 13 stone (70 to 83 kg / 154 to 182 lb), covers the average UK and US adult. Stone-and-pound notation is most useful inside this everyday body-weight range; for newborns and small children pounds-and-ounces or kilograms work better, and for athletes or clinical settings the decimal kilogram is the standard. BMI categories also depend on height, so two people at 14 stone (89 kg / 196 lb) can be in very different BMI brackets.