To convert stone to pounds, multiply by 14. To convert stone to kilograms, multiply by 6.35029318. For example, a mass of 3 stone equals 42 lb, or approximately 19.05 kg. If the starting value includes both stone and pounds, convert the stone part first, then add the remaining pounds.
The detail that causes the most confusion is the notation. A decimal such as 3.5 st means three and a half stone. A mixed entry such as 3 st 5 lb means three stone plus five pounds. Those are different amounts, so identify the format before entering anything into a calculator.
What does one stone equal?
A stone, abbreviated st, contains 14 ordinary pounds. The Open University’s imperial mass reference lists that relationship. The pound used here is the avoirdupois pound, the ordinary mass unit represented by lb.
NIST’s measurement tables give one avoirdupois pound as exactly 0.45359237 kg. Multiplying that value by 14 gives exactly 6.35029318 kg per stone. The shorter figure 6.35 kg is useful for a quick estimate, but it is rounded.
Keep these relationships together: 1 st = 14 lb = 6.35029318 kg. The object has the same mass whichever unit you use. Only the number changes. For the same positive mass, the number of pounds is larger than the number of kilograms, and both are larger than the number of stone.
Convert stone to pounds or kilograms
Pounds = stone × 14.
Kilograms = stone × 6.35029318.
Suppose a storage box has a recorded mass of 2.25 st. Multiplying 2.25 by 14 gives 31.5 lb. Multiplying 2.25 by 6.35029318 gives 14.288159655 kg, or 14.29 kg rounded to two decimal places. These are equivalent descriptions of the same example mass.
You can also go through pounds: 31.5 × 0.45359237 gives the same kilogram result. That route is handy when your starting record contains stone and separate pounds. Avoid rounding the intermediate value if you want the final answer to agree with a direct conversion.
Stone conversion reference table
The pound values below are exact for the stated stone values. Kilograms are rounded to two decimal places. Decimal stone values in this table are fractions of one stone, not an extra pounds field.
| Stone (st) | Pounds (lb) | Kilograms (kg), approximately |
|---|---|---|
| 0.25 | 3.50 | 1.59 |
| 0.5 | 7.0 | 3.18 |
| 1 | 14 | 6.35 |
| 1.5 | 21.0 | 9.53 |
| 2 | 28 | 12.70 |
| 2.5 | 35.0 | 15.88 |
| 3 | 42 | 19.05 |
| 4 | 56 | 25.40 |
| 5 | 70 | 31.75 |
| 10 | 140 | 63.50 |
Convert mixed stone and pounds
For an entry written as S stone and P pounds, calculate total pounds = (S × 14) + P. Then multiply the total by 0.45359237 if you need kilograms. The letters simply stand for the two numbers in your record.
For example, 4 st 9 lb becomes (4 × 14) + 9 = 65 lb. In kilograms, 65 × 0.45359237 = 29.48350405 kg, or about 29.48 kg. Enter the whole expression in parentheses before multiplying, or calculate the pounds total separately.
For a tidy mixed-unit result, the pounds part should be less than 14. A record of 2 st 17 lb can be rewritten as 3 st 3 lb, because 14 of those 17 pounds make another stone. Both descriptions total 45 lb.
Why 3.5 stone is not 3 stone 5 pounds
The decimal point divides whole stone from a fraction of a stone. In 3.5 st, the fractional part is 0.5 st. Multiply that fraction by 14 to get 7 lb. Therefore, 3.5 st equals 3 st 7 lb, or 49 lb altogether.
By comparison, 3 st 5 lb totals 47 lb. Written in decimal stone, it is 3 + (5 ÷ 14), or approximately 3.35714 st. Writing it as 3.5 st silently adds two pounds to the original amount.
Use explicit unit labels when copying a result into notes or a form. If a display uses a colon or a space, check its instructions rather than assuming the separator means a decimal point. Separate st and lb fields require the mixed format; a field requesting decimal stone requires one decimal number.
Convert pounds or kilograms back to stone
Decimal stone = pounds ÷ 14. For mixed stone and pounds, find how many complete groups of 14 fit into the pounds total, then keep the remainder. With 53 lb, three groups account for 42 lb, leaving 11 lb. The result is 3 st 11 lb, or approximately 3.78571 st.
Decimal stone = kilograms ÷ 6.35029318. To express kilograms in mixed units, first divide by 0.45359237 to obtain pounds, then split into groups of 14. For example, 20 kg is approximately 44.09245 lb, which is 3 st 2.09 lb when the remaining pounds are rounded to two decimals.
If you only need the kilogram–pound step, our kilograms-to-pounds guide explains that conversion in more detail.
Round once and label the answer
Keep full precision while calculating, then round the final result to suit your record. If the remaining pounds round to 14, carry them into one more stone and write zero remaining pounds. For example, 2 st 13.96 lb rounds to 3 st 0 lb at the nearest whole pound.
A useful final check is to convert your answer back. Multiply the whole stone by 14, add any remaining pounds, and compare with the original total. Preserve the original measurement alongside the conversion when precision matters; extra calculator digits do not improve the accuracy of the original reading.
For simple arithmetic, you can browse basic desktop calculators on Amazon.
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