Weight Converter
Convert weight between kilograms, pounds and stone.
Pounds
154.32 lb
70 kg
Kilograms
70 kg
Pounds
154.32 lb
Stone
11.02 st
AI Breakdown & Smart Takeaway
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How the Weight Converter works
The Weight Converter instantly converts weight values between kilograms (kg), pounds (lb), and stone — the three most commonly used weight units worldwide. It's ideal for anyone tracking fitness goals, interpreting medical results, shopping internationally, or simply making sense of a weight listed in an unfamiliar unit.
At its core, the Weight Converter applies precise, internationally standardized conversion ratios between three distinct systems: the metric system (kilograms), the imperial/US customary system (pounds), and the British stone system. The kilogram is the SI base unit of mass, defined since 2019 by a fixed numerical value of the Planck constant. One pound is exactly 0.45359237 kilograms by international agreement, and one stone equals exactly 14 pounds — meaning all conversions between these three units can be derived from a single anchor relationship without any approximation error.
The most common conversions people need are kg to lb and pounds to kg. To convert kilograms to pounds, the tool multiplies your input by 2.20462262185, the exact lb-per-kg ratio. Going the other direction — pounds to kg — it multiplies by 0.45359237. Stone conversions add one more step: a stone value is first converted to pounds (multiplying by 14), and then to kilograms if needed. Because stone is a compound unit often expressed as 'stone and pounds' (e.g., 11 st 4 lb), the converter handles fractional stone carefully to avoid the common mistake of treating 0.5 stone as 7.5 lb rather than 7 lb.
A frequent source of confusion is that 'weight' and 'mass' are technically different — weight is a force (affected by gravity) while mass is an intrinsic property — but in everyday use, kilograms, pounds, and stone all measure body mass and are used interchangeably in commerce, health, and fitness contexts. This distinction rarely matters for practical conversions, but it's worth knowing when reading scientific literature. Medically, most countries outside the US and UK use kilograms exclusively, so understanding how to convert is essential when comparing BMI charts, drug dosages (which are often weight-based), or international health records.
Common mistakes when converting weight manually include rounding too aggressively too early (e.g., using 2.2 instead of 2.20462 for kg to lb, which introduces a 0.21% error that compounds across large values), and confusing the stone-and-pounds format with a decimal. For example, 75 kg is approximately 11 st 11.5 lb — not 11.75 stone. Using this calculator eliminates both pitfalls by applying exact ratios and clearly separating stone from its remainder pounds, giving you a result you can trust for medical appointments, shipping weights, or gym tracking.
Formula
1 kg = 2.20462262185 lb | 1 lb = 0.45359237 kg | 1 stone = 14 lb = 6.35029318 kg | kg to lb: multiply by 2.20462 | lb to kg: multiply by 0.45359237 | stone to kg: multiply by 6.35029318
Pro tips
- When tracking body weight over time, always record in the same unit to avoid false trends — a 0.5 kg loss looks different when poorly rounded to pounds across multiple entries.
- If you receive a weight in 'stone and pounds' (e.g., 12 st 3 lb), convert to total pounds first (12 × 14 + 3 = 171 lb) before running the full kg conversion to avoid a common calculation error.
- For medical or pharmaceutical purposes, always use kilograms — drug dosages and clinical thresholds (like BMI cut-offs) are standardised in kg internationally, and using pounds without converting can cause dangerous errors.
- When shipping internationally, note that many carriers bill in kg but quote maximums in lb on their US pages — use this converter to verify you're within both limits before packaging.
- Remember that body weight fluctuates by 1–2 kg (2–4 lb) throughout the day due to food, water, and clothing — weigh yourself consistently (same time, same conditions) for meaningful comparisons regardless of the unit you use.
Key terms
- Kilogram (kg)
- — The SI base unit of mass, used in most countries worldwide for body weight, food, and scientific measurement.
- Pound (lb)
- — The primary unit of weight in the US customary and imperial systems, equal to exactly 0.45359237 kilograms.
- Stone (st)
- — A unit of weight used predominantly in the UK and Ireland, equal to exactly 14 pounds or approximately 6.35 kilograms.
- Stone and Pounds Format
- — The conventional British way to express body weight using both whole stones and remaining pounds (e.g., 11 st 6 lb), rather than a single decimal stone value.
- Conversion Factor
- — A fixed numerical ratio used to transform a measurement from one unit to another without changing the underlying quantity.
- Mass vs. Weight
- — Mass is the intrinsic amount of matter in an object (measured in kg), while weight is the gravitational force acting on it — in everyday use, both terms refer to the same scale readings.
