Converting body weight from stones and pounds to kilograms is a daily need for anyone following a UK or Irish weight-loss plan, reading a fitness app built around imperial units, or comparing health data across countries. The stone (st) is still the standard unit for personal body weight in the UK and Ireland, while nutrition labels, medical records, and most scientific literature use kilograms (kg). This stone to kg conversion calculator gives you an instant, accurate result along with a step-by-step breakdown so you can see exactly how the math works.
Simply enter your weight in stones and pounds — or switch to a single total-pounds input — and the tool returns kilograms with two decimal places, plus the equivalent weight in pounds for easy reference. It also includes quick preset buttons for common body weights like 10 stone, 12 stone, and 14 stone to make repeat conversions even faster. Whether you are tracking macros, adjusting a calorie target, or logging a medical measurement, this converter keeps your numbers consistent and reliable.
⚖️ Stone to Kilogram Converter
Pounds field usually holds 0–13 (the fractional part of a stone).
How to Use This Converter
The stone-to-kilogram converter accepts weight in two complementary ways. In the first row, type a value in stones and a value in pounds — for example, 11 stone 4 pounds. Then press Convert to kg. If you only want to enter a single number, use the total pounds field; the tool will automatically split it into stones and pounds for the breakdown. You can also click a quick preset button (8 st, 10 st, 12 st, 14 st, or 16 st) to instantly load a common body weight and convert it.
A helpful shortcut: if you know your weight in pounds only, enter it in the total-pounds box and press Use pounds field. The calculator fills in the equivalent stones-and-pounds split, which is handy when logging weight from a US scale into a UK-style app. All results are shown to two decimal places in kilograms, with the full working-out displayed underneath so you can verify the conversion by hand if you wish.
Formula & Conversion Method
The imperial stone system defines each stone as exactly 14 pounds (lb). The international avoirdupois pound is defined as exactly 0.45359237 kilograms (kg), a value fixed by international agreement since 1959. Therefore, the conversion from stones to kilograms is:
kg = (stones × 14 + pounds) × 0.45359237
For example, to convert 10 stone 7 pounds: first convert the stone part to pounds (10 × 14 = 140 lb), then add the extra pounds (140 + 7 = 147 lb), and finally multiply by the pound-to-kilogram factor (147 × 0.45359237 = 66.678 kg). The reverse conversion — kilograms to stone — uses the inverse: divide the kilogram value by 6.35029318 to get stones, or by 0.45359237 to get total pounds and then split by 14.
Because 14 is a conveniently round number, the stone-to-pound step never produces a repeating decimal, so the only rounding that appears in the final figure comes from the pound-to-kilogram multiplication. The tool carries full precision internally and only rounds the displayed result to two decimal places, which is more than adequate for body-weight tracking, nutrition planning, and clinical use.
Worked Examples
Example 1: 12 stone exactly. 12 × 14 = 168 lb; 168 × 0.45359237 = 76.2035 kg, rounded to 76.20 kg.
Example 2: 9 stone 10 pounds. 9 × 14 + 10 = 136 lb; 136 × 0.45359237 = 61.6886 kg, rounded to 61.69 kg.
Example 3: A total of 150 lb. 150 ÷ 14 = 10 remaining 10, so this is 10 stone 10 pounds; 150 × 0.45359237 = 68.04 kg.
When to Use Stone vs. Kilogram
In the United Kingdom and Ireland, body weight is almost always stated in stones and pounds, especially in everyday conversation and on bathroom scales. Medical records in the UK often list weight in kilograms, which means patients and practitioners frequently need to switch between the two systems when comparing historical measurements, reading fitness apps, or following hospital dietary guidelines. In the United States, pounds dominate for body weight, while nutrition science, food labeling, and most global health databases use kilograms.
For nutrition and diet planning, staying consistent with one unit is more important than which unit you choose. If your calorie target or macronutrient plan is based on a weight in kilograms, use the kg value from this calculator to compute your basal metabolic rate (BMR) or protein goals. If your scale speaks in stone, keep that number for daily weigh-ins and only convert when a formula requires metric units. This avoids the small rounding errors that creep in when you convert back and forth repeatedly.
Standard Values & Reference Table
The table below lists common body-weight benchmarks in stone with their exact kilogram equivalents, using the factor 1 st = 6.35029318 kg. These are useful for quick mental checks and for verifying the calculator's output.
| Stones | Pounds | Kilograms (kg) |
|---|---|---|
| 8 st | 112 lb | 50.80 kg |
| 9 st | 126 lb | 57.15 kg |
| 10 st | 140 lb | 63.50 kg |
| 11 st | 154 lb | 69.85 kg |
| 12 st | 168 lb | 76.20 kg |
| 13 st | 182 lb | 82.55 kg |
| 14 st | 196 lb | 88.90 kg |
| 15 st | 210 lb | 95.25 kg |
| 16 st | 224 lb | 101.60 kg |
Common Mistakes to Avoid
One frequent error is entering a pound value greater than 13 in the stones-and-pounds row. Since 14 pounds make a full stone, a value like “10 stone 16 pounds” should be normalized to “11 stone 2 pounds.” This converter assumes pounds are between 0 and 13.99; if you type a value of 16, the validation will prompt you to correct it. Use the total-pounds field instead if your source gives you a single pound figure.
Another pitfall is mixing up the conversion factor. Remember that 1 kilogram is about 2.20462 pounds, so 1 stone is about 6.35 kg — not 14 kg. A quick sanity check: a typical adult weighing 11 stone should read about 70 kg on a metric scale. If your result looks off by a factor of two or more, you likely multiplied by 14 instead of by 6.35.
Finally, be careful when rounding intermediate values. If you round the pounds-to-kilograms step prematurely, small errors can accumulate, especially when you use the converted weight for a calorie or macro calculation over several weeks. This tool keeps full precision in the background and only rounds the displayed answer, which is why the step-by-step output may show a slightly different fourth-decimal value than if you rounded each step.
Frequently Asked Questions
Why is the pound-to-kilogram factor exactly 0.45359237? This value was fixed in 1959 by the international yard and pound agreement between English-speaking countries. It is a defined constant, not a measurement, which is why the conversion is always exact up to the precision of your input.
How many kg is one stone? Exactly 14 × 0.45359237 = 6.35029318 kilograms. That is the number to use when converting directly from stone to kg without a pounds component.
Can I use this calculator for baby weights? Yes. Although baby weights are commonly given in pounds and ounces (where 1 lb = 16 oz), you can convert ounces to pounds first (divide by 16) and then enter the result in the pounds field. For example, 8 lb 6 oz becomes 8.375 lb, which is 3.80 kg.
What about the “stone” in cooking? Cooking stones (grain or flour) and the ancient stone weight for trade historically varied by region and commodity. Today, the standard stone used in British body-weight measurement is exactly 14 lb, which is the only version this calculator uses.
Where can I learn more? The UK National Health Service (NHS) provides body mass index (BMI) tools and weight-management guidance that use kilograms; the US National Institute of Standards and Technology (NIST) publishes detailed unit-conversion references for the international yard and pound system.