Weight & Mass Converter
Convert between metric and imperial weight and mass units — milligrams, grams, kilograms, tonnes, ounces, pounds and stones.
About weight & mass conversions
Weight and mass describe how much matter something contains, and the SI base unit is the kilogram — every other unit here is converted through it. Metric units step in exact powers of 1,000, from the milligram to the tonne, so converting inside the metric system never loses precision.
Imperial units are defined against the metric system rather than the other way round: a pound is exactly 0.45359237 kilograms and an ounce is exactly one sixteenth of a pound. The stone survives almost only as a British body-weight unit. For trade it is worth knowing that a metric tonne (1,000 kg) is not a US short ton (907.18 kg) or a UK long ton (1,016.05 kg).
- Body weight — kilograms locally, pounds or stones in imperial countries.
- Market produce and cooking (grams and kilograms).
- Freight, cargo and harvests (tonnes).
- Postal and small-parcel weights (grams and ounces).
Reading the answers. Metric conversions are exact. Results are displayed rounded, so values at the extreme ends of the scale — milligrams and tonnes — carry fewer significant digits than the middle of the range.
The units in this converter
What each unit is and where it is normally used. Everything here is converted through the kilograms.
- Milligrams (mg)
- A milligram is one thousandth of a gram. It is used for medicine doses, laboratory work, water-quality readings and any measurement of trace amounts.
- Grams (g)
- A gram is one thousandth of a kilogram. It is used for food portions, recipe ingredients, jewellery and postal items, and it is the unit most kitchen scales show.
- Kilograms (kg)
- The kilogram is the SI base unit of mass. It is used for body weight, market produce, luggage allowances and cargo, and it is the unit a metric kitchen or market scale shows.
- Tonnes (metric) (t)
- A metric tonne is 1,000 kilograms. It is used for shipping, freight, harvests and industrial quantities. It is not the same as a US short ton (907.18 kg) or a UK long ton (1,016.05 kg).
- Ounces (oz)
- An ounce is exactly 28.349523125 grams, one sixteenth of a pound. It is used for food portions and postal weights, and precious metals use the different troy ounce of 31.1035 g.
- Pounds (lb)
- A pound is exactly 0.45359237 kilograms, or 16 ounces. It is the everyday weight unit in the United States and remains common for body weight and packaged goods elsewhere.
- Stones (st)
- A stone is exactly 14 pounds, or 6.35029318 kilograms. It is used almost exclusively in the UK and Ireland, mainly for body weight.
Tanzania reference points
Real quantities in weight & mass, shown in the units people actually use.
The most a packet declared between 500 g and 1 kg may fall short under Tanzanian weights and measures rules
15 g · 15,000 mg · 0.015 kg · 1.5e-5 t · 0.529109 oz · 0.033069 lb · 0.002362 st
Table IIIC of the 2019 regulations allows an individual deficiency of 1.5%, or 15 g, on a nominal net content between 500 g and 1 kg. Regulation 179 separately requires the average net content of a whole lot to be at least what the packet declares, so the tolerance is on single packets rather than the batch.
Source: The Weights and Measures (General) Regulations, 2019 (GN No. 288) — Weights and Measures Agency · verified 2026-09-14
Popular conversions
Convert from any weight & mass unit
Each unit has its own page with every other unit in the dimension, the exact factor for each, and worked values.
Frequently asked questions
How many pounds are in a kilogram?
One kilogram equals approximately 2.20462 pounds. To convert kilograms to pounds, multiply by 2.20462.
How many grams are in an ounce?
One ounce equals exactly 28.349523125 grams. To convert ounces to grams, multiply by 28.349523125.
How many pounds are in a stone?
One stone equals exactly 14 pounds. To convert stones to pounds, multiply by 14.
All weight & mass conversions
Every weight & mass conversion on Calculator, listed in full.
- Milligrams to Grams
- Milligrams to Kilograms
- Milligrams to Tonnes (metric)
- Milligrams to Ounces
- Milligrams to Pounds
- Milligrams to Stones
- Grams to Milligrams
- Grams to Kilograms
- Grams to Tonnes (metric)
- Grams to Ounces
- Grams to Pounds
- Grams to Stones
- Kilograms to Milligrams
- Kilograms to Grams
- Kilograms to Tonnes (metric)
- Kilograms to Ounces
- Kilograms to Pounds
- Kilograms to Stones
- Tonnes (metric) to Milligrams
- Tonnes (metric) to Grams
- Tonnes (metric) to Kilograms
- Tonnes (metric) to Ounces
- Tonnes (metric) to Pounds
- Tonnes (metric) to Stones
- Ounces to Milligrams
- Ounces to Grams
- Ounces to Kilograms
- Ounces to Tonnes (metric)
- Ounces to Pounds
- Ounces to Stones
- Pounds to Milligrams
- Pounds to Grams
- Pounds to Kilograms
- Pounds to Tonnes (metric)
- Pounds to Ounces
- Pounds to Stones
- Stones to Milligrams
- Stones to Grams
- Stones to Kilograms
- Stones to Tonnes (metric)
- Stones to Ounces
- Stones to Pounds
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