How weight units relate to each other
Weight is measured in two common systems. The metric system is built around the gram and the kilogram, with a milligram being one thousandth of a gram and a kilogram being one thousand grams. The imperial and US customary system uses ounces and pounds, where 16 ounces make one pound.
To move between the systems you need a conversion factor. This tool uses the kilogram as its internal base unit. It converts your value into kilograms first, then divides by the factor of the unit you want. The factors it uses are 0.000001 kg per milligram, 0.001 kg per gram, 0.0283495 kg per ounce, 0.453592 kg per pound, and 1000 kg per ton.
Everyday situations where you need to convert
Weight conversions come up in cooking, shipping and travel. A recipe written in ounces may need grams for your kitchen scale, and a parcel service may quote limits in pounds while your scale reads kilograms. When you need lengths or liquid amounts instead, the Length Converter and Volume Converter work in the same way.
How to convert weight with this tool
- On the page, use the From number box to enter the value. It starts at 1.
- Pick the starting unit in the select list under it. The choices are Milligrams, Grams, Kilograms, Ounces, Pounds and Tons.
- Pick the unit you want in the list under To. The page starts with Milligrams to Grams.
- Read the answer in the result box. It updates immediately, with no Convert button.
For example, 16 ounces to kilograms gives 0.453592 and 5 pounds to kilograms gives 2.26796. A value entered in tons is read as 1000 kg per ton, so 1 ton to kilograms returns 1000. Results are rounded to six decimal places. There is no copy button or swap button, so select the result text yourself or reselect the units.
Accuracy, tons and other cautions
The ton here is the metric ton (also called a tonne), equal to 1000 kilograms. It is not the US short ton of 2000 pounds, nor the UK long ton. If a source says "ton" in an American context, the numbers will not match this tool, so check which one is meant.
The ounce and pound factors are rounded, which is plenty for cooking, shopping and shipping but not intended for laboratory or legal measurement. The tool also rounds its answer to six decimal places, so very small amounts in large units may show as 0.
Ounces here are weight (avoirdupois) ounces. They are not the fluid ounces used for liquids, which measure volume and cannot be converted to weight without knowing the substance. The calculation runs in your browser as you type.