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Weight and Mass Converter

Quick picks

Result

1 Kilograms (kg) = 2.20462 Pounds (lb)

Estimates for educational purposes — not financial, medical, or legal advice. See terms.

Convert any mass value between eight units: milligrams, grams, kilograms, tonnes, ounces, pounds, stones, and carats. Both sides are editable — type into either and the other updates. Swap button flips the direction. Five quick-pick buttons jump to common pairs (kg ↔ lb, g ↔ oz, stone ↔ lb).

Exact conversion factors

All imperial / US-customary units derive from the 1959 International Yard and Pound Agreement:

  • 1 pound = 0.45359237 kg (exact)
  • 1 ounce = 1 lb / 16 = 0.028349523125 kg (exact)
  • 1 stone = 14 lb = 6.35029318 kg (exact)

Metric units are exact powers of ten of the kilogram. The carat is 200 mg exactly (1907 standardisation). The only “approximate” derived values you’ll see come from floating-point representation of the conversion results, not from the factors themselves.

Example: body weight between units

70 kg in pounds: 70 × 2.20462 ≈ 154.32 lb. In stones: 154.32 / 14 ≈ 11.02 stone. For a UK audience, that’d be announced as “11 stone 0.3” — 11 × 14 = 154 lb, plus 0.32 lb × 16 ≈ 5 oz. The tool gives you the single-unit value; composite “stones + pounds” display needs manual conversion.

Example: cooking scales

Many US recipes use ounces for small quantities (butter, cheese, chocolate). 4 oz = 113.4 g — handy when you’re using a kitchen scale calibrated in grams but the recipe calls for ounces. 1 stick of US butter is 4 oz = 113.4 g. 1 cup of all-purpose flour is about 120–125 g depending on how packed it is.

Example: freight and shipping

1 tonne = 1000 kg = 2204.62 lb. UPS and FedEx bill in lb; European freight bills in tonnes. A 500 kg package is 0.5 tonnes or 1102.3 lb. Shipping carriers use dimensional weight for bulky-light packages, but the mass conversion is still the first step.

Short ton, long ton, metric tonne

Three different “tons”:

  • Metric tonne: 1000 kg exactly. The SI-compatible unit.
  • Short ton (US): 2000 lb = 907.18474 kg.
  • Long ton (UK): 2240 lb = 1016.0469088 kg.

The tool includes only the metric tonne because the short/long distinction is a common source of error and both are losing ground to the unambiguous metric tonne. For a US context, if someone says “ton” they usually mean short ton; in UK shipping they usually mean long ton; in scientific context they always mean metric tonne.

What this tool does not do

It doesn’t handle mixed units like “8 lb 6 oz” or “11 stone 4 lb”. Each component needs separate conversion and summation. A dedicated imperial-body-weight tool handles composite input. For cooking recipes in volume units instead of mass, the volume converter is the counterpart.

It doesn’t include ambiguous tons. Only the metric tonne is in the table. For short/long tons, convert to pounds as an intermediate.

It doesn’t compute BMI, weight gain/loss, or anything medical. It’s a pure unit converter.

It doesn’t handle weight-as-force (newtons, pound-force). For force conversion you need gravitational acceleration, which depends on location.

It doesn’t support apothecary or troy units (grain, dram, pennyweight, troy ounce). Precious-metal markets use troy ounces (31.1035 g, different from avoirdupois ounces). If you’re pricing gold, you need a separate troy-specific converter.

Frequently asked questions

Is the 'weight' here actually mass?

Yes. In everyday language, 'weight' is measured in kg, lb, and so on — but those are strictly mass units. Physical weight (the downward force on a body from gravity) is measured in newtons, and would differ between Earth, the Moon, and Mars even for the same object. This tool converts between mass units — what bathroom scales, grocery-store produce, and shipping carriers measure. If you genuinely need weight-as-force, use a force converter and multiply by local gravitational acceleration.

Why is the pound exactly 0.45359237 kg?

Because that's the value fixed by the 1959 International Yard and Pound Agreement between the English-speaking countries (US, UK, Canada, Australia, New Zealand, South Africa). Before 1959, each country had its own slightly different 'pound' defined in different ways. The agreement picked a single exact value, and every imperial / US-customary unit (ounce, stone, ton, etc.) is derived from it by exact integer ratios — ounce = lb / 16, stone = 14 lb, pound-based ton = 2000 lb.

What's a stone?

A British unit equal to 14 pounds, or about 6.35 kg. Still widely used in the UK and Ireland for body weight and sometimes larger objects (livestock, household goods). 'Ten stone' is a natural-language weight that maps to 140 lb or 63.5 kg. When British people give their weight in casual conversation, it's almost always in stones and pounds (e.g., 'I'm 11 stone 4', meaning 11 × 14 + 4 = 158 lb).

What's a carat?

A metric unit equal to exactly 200 milligrams (0.0002 kg), used almost exclusively for gemstones and pearls. 5 carats = 1 gram. Don't confuse it with karat (gold purity), which is spelled differently and measures parts-per-24 of pure gold content rather than mass. The metric carat was standardised in 1907; before that, carat values varied regionally between about 188 mg and 213 mg.

Does the tool distinguish short ton, long ton, and metric tonne?

Only the metric tonne (1000 kg) is included, because it's the most unambiguous. Short ton (US, 2000 lb ≈ 907.18 kg) and long ton (UK, 2240 lb ≈ 1016.05 kg) are also valid units but create confusion when not labelled. If you need those, convert to pounds first (short ton × 2000 or long ton × 2240), then convert to kg. A more feature-complete tool could expose all three; this one keeps the list short and unambiguous.