Pounds to Stone
Convert pounds to stone with the exact factor (1 lb = 1/14 st), a quick reference table, and common body-weight examples in UK units.
lb to st formula
To convert pounds (lb) to stone (st), divide by 14, because 1 stone = 14 pounds exactly.
Quick reference: lb to st
Common values
1 lb = 0.071 st
10 lb = 0.714 st
100 lb = 7.14 st
140 lb = 10 st
200 lb = 14.29 st
Worked example
Convert 140 lb to stone:
140 lb ÷ 14 = 10 st
So 140 lb is exactly 10 stone.
Why convert lb to st?
Body weight in the UK is usually given in stone and pounds, while the US uses pounds. This conversion lets you read UK weights on a US scale.
You can also use our calculator or read the paired guide st reference.
Frequently Asked Questions
How many stone are in a pound?
1 lb = 1/14 st ≈ 0.0714286 st.
How many pounds are in a stone?
1 stone = 14 pounds exactly.
How do I convert 150 lb to stone?
150 lb ÷ 14 ≈ 10.71 st (10 st 10 lb).
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Quick Summary
lb to st uses a single exact factor. Use the formula above or the reference table for quick, accurate results.
Related Guide
Stones to Pounds: Convert UK Stone Weight to US Pounds
Convert stones to pounds with the exact factor. 1 stone equals 14 lbs. See the math, UK fitness context, and a quick reference table.
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Disclaimer
Unit conversions on this site use internationally recognized, fixed conversion factors (for example, 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 °F = (°C × 9/5) + 32). They are provided for general, informational, and educational use. For applications where accuracy is critical — such as medical dosing, engineering, scientific research, trade, or legal compliance — always verify results against authoritative sources such as the U.S. National Institute of Standards and Technology (NIST) and the official International System of Units (SI) brochure, and follow any applicable local standards.
Exact Constants & Authoritative Sources
Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.
- EXACT1 pound (lb, avoirdupois) = 0.45359237 kilograms (exact)
- EXACT1 ounce (oz, avoirdupois) = 28.349523125 grams (exact, 1/16 lb)
- EXACT1 stone (st) = 6.35029318 kilograms (exact, 14 lb)
- EXACT1 short ton (US) = 907.18474 kilograms (exact, 2000 lb)
Common Pitfalls & How to Avoid Them
Mass vs. weight
The pound and kilogram are units of MASS, not force. On Earth, mass and "weight" read the same number in practice, but a 70 kg mass weighs less on the Moon. UnitFig converts mass; for scientific force you need newtons (1 lbf = 4.4482216152605 N, exact).
Avoirdupois vs. troy ounce
Cooking and body weight use the avoirdupois ounce (28.349523125 g). Gold and precious metals use the troy ounce (31.1034768 g). Never mix them — the error is about 10%.
Rounding the factor
Using 2.2 instead of the exact 2.20462262 overstates small errors at large values. For medical dosing or competition weight classes, keep the full factor or use a converter.
A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.
Authoritative sources for this page
- NIST (U.S. National Institute of Standards and Technology) — NIST SP 330 — The International System of Units (SI), 2019 edition
Last Updated 2026 | This article was reviewed for accuracy