What the Weight & Mass Converter Does

This weight and mass converter changes a value from one unit to another across the units people use most: kilograms (kg), grams (g), pounds (lb), ounces (oz), stones (st), and tons. Enter a number, pick the unit you have and the unit you want, and the result is calculated instantly.

It's useful for cooking and recipes, shipping and parcel weights, gym and bodyweight tracking, lab and school work, and any time you need to move between metric and imperial units. If you regularly do kg to lbs or grams to ounces, this tool removes the guesswork.

How the Mass Converter Works (The Formula)

Every conversion uses kilograms as a common base unit. The tool first converts your input to kilograms, then converts kilograms to the target unit. This two-step method keeps results consistent no matter which pair of units you choose.

The core conversion factors are:

1 pound (lb) = 0.45359237 kg (often rounded to 0.4536 kg)
1 ounce (oz) = 28.3495 g (about 28.35 g)
1 stone (st) = 6.35029 kg
1 gram (g) = 0.001 kg
1 metric ton (tonne) = 1,000 kg

Worked Example: Convert 70 kg to Pounds and Stones

Suppose you weigh 70 kg and want the value in pounds. Divide by the kilograms-per-pound factor: 70 / 0.45359237 = 154.32 lb.

To get stones, divide by 6.35029: 70 / 6.35029 = 11.02 stone. In the UK, body weight is usually given in stones and pounds, so 11.02 stone is read as 11 stone 0.3 pounds, or roughly 11 st 0 lb. Converting the other way, 154.32 lb x 0.45359237 = 70 kg, confirming the result.

Tips and Common Mistakes

Most errors come from mixing up similar-sounding units. Keep these points in mind:

Watch ton definitions: a metric ton (tonne) is 1,000 kg, a US (short) ton is about 907.18 kg, and a UK (long) ton is about 1,016.05 kg. Confirm which one you need.
Don't confuse fluid ounces (volume) with ounces (mass) — this converter handles mass only.
A stone is 14 pounds. When a result shows 11.5 stone, the 0.5 means 7 pounds, not 50 pounds.
Round only at the end. Rounding mid-calculation, especially with the 0.4536 approximation, can shift large values noticeably.

Mass vs. Weight: A Quick Note

Strictly speaking, mass is the amount of matter in an object (measured in kilograms or grams), while weight is the force gravity exerts on that mass (measured in newtons). On Earth's surface gravity is nearly constant, so everyday units like kilograms and pounds are used for both, and the two terms are treated as interchangeable in daily life.

The distinction matters in physics or off-Earth contexts: an object's mass stays the same on the Moon, but its weight is about one-sixth of its Earth weight because gravity is weaker. This converter works with mass values, which hold true regardless of location.