Weight Converter
Convert between milligrams, grams, kilograms, tons, ounces, pounds, stone and more.
Weight vs. mass: what is the difference?
In everyday language, "weight" and "mass" are used interchangeably — but they are physically distinct. Mass is the amount of matter in an object, measured in kilograms (kg). It does not change regardless of location. Weight is the gravitational force acting on that mass, measured in newtons (N). On the Moon, your mass stays the same, but your weight drops to about one-sixth of what it is on Earth.
In practice, bathroom scales, food labels, and shipping invoices all deal with mass, even when they say "weight." This converter uses the conventional meaning: all units refer to mass, with kilograms as the base.
How weight conversion works
Every unit is expressed as a fixed number of kilograms. The formula is:
Result = Input × (From unit in kg) ÷ (To unit in kg)Worked examples:
Convert 150 pounds to kilograms:
150 × 0.453592 ÷ 1 = 68.04 kg
Convert 80 kg to stone:
80 × 1 ÷ 6.35029 = 12.60 st
Convert 500 grams to ounces:
500 × 0.001 ÷ 0.0283495 = 17.64 ozUnit reference table
| Unit | Exact value in kg | Primarily used in |
|---|---|---|
| Milligram (mg) | 0.000001 kg | Pharmaceuticals, nutritional supplements |
| Gram (g) | 0.001 kg | Food portions, postal items, precious metals |
| Kilogram (kg) | 1 kg (base unit) | Global standard for body weight, goods |
| Metric ton (t) | 1,000 kg | Cargo, industrial materials, agriculture |
| Ounce (oz) | ≈ 0.02835 kg | US food labels, postal parcels |
| Pound (lb) | ≈ 0.4536 kg | US body weight, US grocery items |
| Stone (st) | ≈ 6.350 kg | Body weight in the UK and Ireland |
| US Ton (short ton) | ≈ 907.2 kg | US freight, construction materials |
Common real-world uses
The stone: a uniquely British unit
Stone (st) is a unit used almost exclusively in the United Kingdom and Ireland for measuring body weight. One stone equals exactly 14 pounds or approximately 6.35 kg. While the UK officially adopted the metric system, stone remains culturally embedded: British people typically describe their weight as "11 stone 4" rather than 71.7 kg or 157 lb.
Outside body weight, stone is rarely used in modern commerce or science. If you see a stone measurement in any other context, it almost certainly refers to a historical document or a regional oddity.
Tips for avoiding common weight conversion errors
- Troy ounce vs. avoirdupois ounce. Gold, silver, and gemstones use the troy ounce (31.1035 g). Everyday items use the avoirdupois ounce (28.3495 g). They differ by about 10%. Using the wrong one in precious metal calculations can cause significant pricing errors.
- Metric ton vs. US ton vs. imperial ton. A metric ton (tonne) = 1,000 kg. A US short ton = 907 kg. A UK long ton = 1,016 kg. In international trade, always clarify which "ton" is meant — the difference is over 100 kg per unit.
- Pounds and kilograms in medical contexts. Drug dosages are almost always expressed per kilogram. A US patient giving their weight in pounds must first convert to kg. At 2.205 lb per kg, a 200 lb patient weighs about 90.7 kg — not 100 kg, which a rounded estimate might suggest.
- Net vs. gross weight in shipping. Conversion accuracy matters more when the declared weight affects customs duties or freight costs. Always weigh items directly rather than estimating, and convert using precise factors rather than rounded approximations.
Frequently asked questions
How many pounds are in a kilogram?
One kilogram equals about 2.205 pounds. To convert kg to lbs, multiply by 2.205; to go from lbs to kg, divide by 2.205.
How do I convert ounces to grams?
Multiply ounces by 28.35. For example, 4 oz × 28.35 = 113.4 grams.
What is a stone in weight?
A stone is a British unit equal to 14 pounds, or about 6.35 kilograms. It is still commonly used for body weight in the UK and Ireland.
Is weight the same as mass?
In everyday use the terms are interchangeable, but strictly, mass is the amount of matter (kg) while weight is the force of gravity on that mass. This tool converts mass units.
Converts weight between 8 units: milligrams, grams, kilograms, metric tons, ounces, pounds, stone and US tons.
All weights convert through kilograms as base unit. Click any tile to use that value as new input.