Weight Conversion Calculator

Weight Conversion Calculator: convert weight conversion instantly. Full formula, unit table, and worked example.

A weight (mass) converter switches between metric units (milligrams, grams, kilograms, tonnes) and imperial/US customary units (ounces, pounds, stones, US tons, long tons), as well as troy units used for precious metals (troy ounces, troy pounds). In everyday US usage, "weight" and "mass" are used interchangeably — technically, weight is a force (Newtons) and mass is matter content (kilograms), but the distinction matters only in physics and engineering contexts.

Weight conversions are needed for cooking recipes, international shipping and freight, body weight tracking, precious metal pricing, pharmaceutical dosing, and scientific laboratory work.

Enter the weight value and select the source unit.
The converter shows equivalents in all common systems simultaneously.
For precious metals (gold, silver, platinum): use troy ounces — 1 troy oz = 31.103 g (heavier than the regular avoirdupois ounce of 28.350 g).

Key weight conversion factors

1 pound (lb) = 453.592 grams = 16 ounces (avoirdupois)

1 kilogram = 2.20462 pounds = 35.274 ounces

1 stone = 14 pounds = 6.350 kg (used for body weight in UK and Ireland)

1 US ton (short ton) = 2,000 lb = 907.185 kg | 1 metric tonne = 1,000 kg = 2,204.62 lb

1 troy ounce = 31.1035 g (gold, silver, platinum pricing standard)

Weight conversion reference

Common weight benchmarks

Body weight: 150 lb = 68.0 kg; 180 lb = 81.6 kg; 200 lb = 90.7 kg. Food portions: 1 oz ≈ 28 g; 1 cup of flour ≈ 120–130 g; 1 lb of butter = 454 g. Shipping: 1 US ton = 2,000 lb = 907 kg; ocean freight often quoted in metric tonnes (1,000 kg). Pharmaceutical: 1 mg = 0.001 g; drug doses in mcg (micrograms) = millionths of a gram. Gold price quoted per troy ounce — standard gold bar (400 troy oz) weighs approximately 12.44 kg (27.4 lb).

Conversion tips and best practices

For quick kg to lb: multiply kg by 2.2 (actual factor 2.205 — close enough for body weight).
For quick lb to kg: divide by 2.2, or multiply by 0.454.
In cooking, weight measurements are far more accurate than volume for baking — 1 cup of flour can weigh 110–145 g depending on packing; weighing in grams gives consistent results.
Precious metal prices are quoted per troy ounce — always use troy ounces for gold, silver, and platinum calculations, NOT regular ounces.

The average American male weighs approximately 197.9 lb (89.8 kg); the average American female weighs approximately 170.6 lb (77.4 kg) — both above the healthy BMI threshold for most height ranges (CDC, 2022).
A standard gold bar (Good Delivery bar) weighs 400 troy ounces = 12.441 kg = 27.43 lb — worth approximately $750,000 at $1,900/troy oz.
The heaviest vehicle in the US highway system (fully loaded semi-truck) legally weighs up to 80,000 lb (36.3 metric tonnes) on most interstate highways.

Common mistakes to avoid

Confusing troy ounces and avoirdupois ounces for precious metals — using the regular ounce (28.35 g) instead of troy ounce (31.10 g) when pricing gold understates the weight by about 9%.
Mixing up US tons (short tons, 2,000 lb) and metric tonnes (2,204.62 lb) in freight and commodities pricing — a difference of approximately 10%.
Using grams when milligrams are needed in pharmaceutical contexts — a dosing error of 1,000× is dangerous; always confirm units in medical and pharmaceutical calculations.

Weight conversions are exact mathematical relationships. For commercial transactions, trade weights are governed by the National Institute of Standards and Technology (NIST) Handbook 44. Pharmaceutical dosing must follow FDA-approved product labelling — never adjust dosing calculations without consulting a licensed pharmacist or physician.