Weight Converter (kg, lb, oz, st, g)

Convert between kilograms, pounds, ounces, stones, grams and tonnes instantly. Type into either box and the other updates, and the exact conversion factor used is shown beneath the result so you can check it. Everything is calculated in your browser.

How to use it

Enter a valueType your number into either box. The other side updates as you type, so conversion works in both directions.
Choose the unitsPick your units from the two dropdowns, or press Swap units to reverse the conversion.
Check the factorThe line beneath the result shows the exact factor applied, for example 1 kg = 2.20462262 lb.

Exact factors, not approximations

Most of the conversions on this page are exact by definition rather than by measurement. The international yard and pound agreement, signed in 1959 by the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa, fixed the pound at exactly 0.45359237 kilograms. Everything in the imperial weight system follows from that single number: an ounce is a sixteenth of a pound, a stone is fourteen pounds, a US short ton is two thousand.

Because those relationships are exact, there is no reason for a converter to use a rounded factor. This one stores the full definition and does the arithmetic in double precision, rounding only the number it puts on screen. In practice that means chained conversions behave: go from kilograms to pounds to ounces and back and you land on the value you started with.

Which unit is used where

The kilogram is the base unit of mass in the International System and is standard almost everywhere for trade, science and medicine. The pound remains in general use in the United States, and alongside metric units in the United Kingdom. The stone survives almost exclusively for body weight in the UK and Ireland, which is why British medical records often carry both a stone-and-pounds figure and a kilogram one.

Grams dominate cooking and postage outside the US, ounces inside it, which is the single most common reason people reach for a converter — a recipe written in one system and a kitchen scale calibrated in the other.

Common conversions

1 kilogram = 2.20462262 pounds
1 pound = 0.45359237 kilograms (exact)
1 stone = 6.35029318 kilograms (exact)
1 ounce = 28.349523125 grams (exact)
1 tonne = 1,000 kilograms (exact)
1 US short ton = 907.18474 kilograms (exact)

Limitations

This converter handles mass only. It will not convert a weight to a volume — a kilogram of flour and a kilogram of water occupy very different amounts of space, and doing that conversion needs the density of the specific substance. It also uses the avoirdupois ounce throughout, so it is the wrong tool for precious metals, which are priced in troy ounces.

Everything runs in your browser. The factors ship with the page, nothing is uploaded, and the tool keeps working if your connection drops.

Frequently asked questions

How many pounds is one kilogram?

One kilogram is approximately 2.20462262 pounds. The relationship is defined in the other direction: one pound is exactly 0.45359237 kilograms, fixed by the 1959 international yard and pound agreement, so the kilogram-to-pound figure is that exact value inverted and then rounded for display.

How many kilograms is one stone?

One stone is 14 pounds, which is exactly 6.35029318 kilograms. The stone is still in everyday use for body weight in the UK and Ireland and almost nowhere else, which is why weights there are often given as, for example, 11 stone 4 pounds.

What is the difference between a tonne and a ton?

A tonne, sometimes called a metric ton, is exactly 1,000 kilograms. A US short ton is 2,000 pounds, about 907 kg. A UK long ton is 2,240 pounds, about 1,016 kg. All three are listed separately here because the difference is large enough to matter in shipping and freight.

Is an ounce always the same?

The ounce in this tool is the avoirdupois ounce, exactly 28.349523125 grams, which is the one used for food, post and general weight. The troy ounce used for precious metals is different at about 31.10 grams — do not use this converter for gold prices.

Why is the result rounded?

Only the display is rounded, to keep everyday answers readable. The calculation itself uses the exact factor at full precision, so converting back and forth returns you to your original number.

Weight or mass?

Strictly these units measure mass, not weight — weight is a force and varies with gravity. In everyday and commercial use the two words are used interchangeably, and the conversions here are the ones people mean when they say weight.

Does this work offline?

Yes. The conversion factors are part of the page and the arithmetic runs on your device, so once the page has loaded no connection is needed.