What is Mass Conversion?
Convert kilograms, grams, pounds, ounces, and more.
Supported units: Kilogram (kg), Gram (g), Milligram (mg), Pound (lb), Ounce (oz).
The kilogram and the pound: two very different journeys
For 130 years the kilogram was defined by a physical object — the "International Prototype Kilogram" (IPK), a platinum-iridium cylinder kept in a vault in Sèvres, France. Every other kilogram in the world was calibrated against it. The problem: the IPK's mass was slowly drifting by tens of micrograms over time, which is unacceptable for a universal standard. In May 2019 the SI system was redefined so the kilogram is now based on a fixed value of the Planck constant (h = 6.62607015 × 10⁻³⁴ J·s), measured with a Kibble balance. The pound has a much older story: from the Roman libra (originally 12 unciae, about 329 g), through many regional variants, to the 1959 international avoirdupois pound — agreed by the US, UK, Australia, Canada, New Zealand, and South Africa to equal exactly 0.45359237 kg. That "international pound" is what every kitchen scale, postal label, and conversion tool — including this one — uses today.
Where you convert mass every day
Shipping, aviation, and logistics
Airlines list baggage limits in kilograms (23 kg checked, 7–10 kg cabin); US domestic carriers mix pounds (50 lb). Freight forwarders deal with cargo quoted in metric tonnes and short tons daily.
Cooking and baking
American recipes use cups and ounces; European and Asian recipes use grams. Precise baking especially needs mass conversion — 1 cup of flour = 125 g (sifted) but 150 g (spooned), a 20% difference that ruins a recipe.
Medicine and fitness
Drug doses are per kilogram of body weight worldwide, so US patients must convert lb → kg for accurate dosing. Gyms list dumbbell weights in both lb and kg; tracking progress requires consistent units.
Precious metals and commodities
Gold and silver are priced per troy ounce (31.1035 g) — not the regular avoirdupois ounce (28.3495 g). Coffee is traded in pounds on New York futures but sold by 250 g / 500 g / 1 kg bags in cafés. Mixing units here costs real money.
Science and engineering
Chemistry uses molar mass in grams per mole; mechanical engineers spec motor torque per kilogram and per pound. Any international R&D team ends up converting datasheets between systems.
Common Conversions
- 1 Kilogram (kg) = 1000 Gram (g)
- 1 Kilogram (kg) = 1000000 Milligram (mg)
- 1 Gram (g) = 0.001 Kilogram (kg)
- 1 Gram (g) = 1000 Milligram (mg)
- 1 Milligram (mg) = 0.000001 Kilogram (kg)
- 1 Milligram (mg) = 0.001 Gram (g)
FAQ
Q: How many grams in 1 kilogram?
A: 1 kilogram = 1,000 grams.
Q: How to convert kg to pounds?
A: Multiply by 2.20462. Example: 70 kg × 2.20462 ≈ 154.3 lb.
Q: How many ounces in 1 pound?
A: 1 pound = 16 ounces.
Q: What's the difference between mass and weight?
A: Mass is how much matter an object contains (measured in kg or lb); weight is the force gravity exerts on that mass (measured in newtons). On Earth the two are proportional, so everyday language uses them interchangeably — but a 70 kg astronaut weighs only ~12 kg-force on the Moon.
Q: Why is a "troy ounce" different from a regular ounce?
A: The troy ounce (31.1035 g) is used exclusively for precious metals — gold, silver, platinum — and has a Roman origin (troy pound = 12 troy ounces, whereas avoirdupois pound = 16 avoirdupois ounces). A bar of gold quoted at 1 oz is about 10% heavier than a "regular" ounce, so always check which one a spot price refers to.