Stone to Pounds Converter

Stone to pounds converter: convert stone to pounds and kilograms instantly, with the formula shown for any value. Free, private, runs locally in your browser.

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Last verified July 2026

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What does this converter do?

Stone to pounds converter: convert stone to pounds and kilograms instantly, with the formula shown for any value. Free, private, runs locally in your browser.

  • 1 pound = 0.4536 kilogram · 1 stone = 6.35 kilogram · 1 ounce = 28.35 gram
  • All conversions route through the kilogram as the base unit, so every pair of units agrees regardless of which two you enter.
  • Standard factors are shown in the formula panel at the precision the calculator actually uses, so the arithmetic and the panel agree.
Bar chart comparing pound totals for common weight conversions
100 kg reads 220.46 lb, a rounding gap of only 0.006 lb.

Reference factors (mass)

Exact factors in terms of the kilogram, from NIST standards:

  • 1 milligram = 1e-06 kilogram
  • 1 gram = 0.001 kilogram
  • 1 ounce = 0.0283495 kilogram
  • 1 pound = 0.453592 kilogram
  • 1 kilogram = 1 kilogram
  • 1 stone = 6.35029 kilogram
  • 1 metric ton = 1000 kilogram
Formula & evidence

How this calculator works

Reviewed 2026-09-20 · BoringToolsKit Editorial Team

Formula

Converts to pounds first (stone x 14, pound x 1, kilogram x 2.20462), then divides: stone = pounds / 14 and kilograms = pounds / 2.20462.

Worked example

1 pound = 0.4536 kilogram · 1 stone = 6.35 kilogram · 1 ounce = 28.35 gram

Sources

Sources support the method, terminology, or planning context. Editable assumptions remain your responsibility.

Assumptions to verify

  • Inputs are treated as exact decimal values.
  • Standard (not historical or survey) unit definitions are used.
  • The calculation uses the factors at the precision shown in the formula panel; rounding beyond that is display-only and adds no accuracy.

Frequently asked questions

Why convert through kilogram instead of directly?

Routing every unit through a single base (kilogram) means each unit needs only one exact factor against the standard, and any pair combines cleanly. Direct pair factors drift apart over time in hand-maintained tables; a base-unit graph cannot.

Where do these exact factors come from?

From published standards (NIST: SI SP 330 mass definitions). Units like the inch are defined exactly (1 in = 2.54 cm since 1959), so conversions between standard units are exact, not approximate.

How many decimal places should I trust?

The math is exact to the precision shown. The practical limit is your input: a tape measure is only good to ~1 mm and a kitchen scale to ~1 g, so 3–4 significant figures already exceeds the measurement's own accuracy.

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Cite this tool

BoringToolsKit. “Stone to Pounds Converter.” boringtoolskit.com/stone-pounds-converter/ (reviewed 2026-09-20). Free to reference in articles, syllabi, and answer posts with a link.

Privacy: Inputs and results stay in this browser. Conversion runs locally in your browser; review the output before relying on it.

Worked example: converting 180 pounds

Enter 180 and choose pounds as the starting unit. The tool multiplies 180 by 1 to get 180 lb, then divides by 14 for stone: 180 / 14 = 12.857, shown as 12.9 stone. For kilograms it divides 180 by 2.20462, giving 81.6466, shown as 81.6 kg.

Now try 13 stone entered directly. That multiplies by 14 to give 182 lb, and 182 / 2.20462 gives 82.5546 kg, displayed as 82.6 kg. Notice the stone figure reads back as exactly 13.0 because stone is the base the calculator divides into, while a value like 12.9 stone entered back would produce 180.6 lb, one decimal place of drift from the original 180.

The same logic runs the other way for kilograms: 80 kg multiplies by 2.20462 to reach 176.3696 lb, which is 12.5978 stone, rounded to 12.6 stone. If you need an exact split for a US-vs-UK weight table, convert to pounds first, then take the whole pounds as the stone remainder: 176 lb is 12 stone 8 lb, since 12 x 14 = 168 and 176 - 168 = 8.

Rounding, exact fractions, and where this breaks down

Every output is rounded to one decimal place, so a stone value shown as 12.9 could really be anywhere from 12.85 to 12.949, a spread of about 1.4 lb. If you need a precise stone-and-pounds figure, work in whole pounds and split manually rather than re-entering the rounded decimal, because each round trip through the converter can add up to 0.05 stone of error.

The kilogram factor is fixed at 2.20462. The exact avoirdupois definition is 1 kg = 2.20462262185 lb, so a 100 kg conversion reads 220.46 lb here versus 220.4623 lb exact, a difference of roughly 0.006 lb. That is invisible on a bathroom scale but not on a calibrated trade scale, where legal-for-commerce conversions use their own certified factors.

Stone is only customary for body weight in the UK and Ireland; it is not a legal unit in the US, and US medical records log pounds or kilograms only. Also, stone measures mass, not force: a 14 lb object weighs 14 lb-force only at standard Earth gravity, so the converter is wrong for scale readings taken on the Moon (about 2.3 lb for the same person) or in accelerating lifts.