Weight & Mass Converter - kg, lb, oz, g, Stone, Tonne

Weight & Mass Converter – kg, lb, oz, g, Stone, Tonne

What Is Weight Conversion?

Weight and mass conversion is the process of expressing the same physical quantity in different units. Whether you're comparing a recipe from a US cookbook to your European kitchen scale, checking if a parcel meets a carrier's weight limit, or tracking your fitness progress between gym visits, the numbers only make sense when they're in the same unit.

This converter handles the seven most commonly used weight and mass units: milligrams (mg), grams (g), kilograms (kg), ounces (oz), pounds (lb), stone (st), and metric tonnes (t). Enter any value, select your starting unit and target unit, and the result appears instantly along with the full equivalency table.

The Units Explained

Metric system (grams as the base):

Milligrams are used for very small quantities — pharmaceutical dosages, food nutrition labels, or laboratory measurements. There are 1,000 milligrams in one gram. Grams are the everyday cooking and baking unit throughout most of the world: 250 g of flour, 100 g of sugar, 28 g of protein per serving. Kilograms are the standard for body weight, grocery shopping, and freight in metric countries. One kilogram equals 1,000 grams. Metric tonnes (spelled with an "e" to distinguish from the US short ton) are used for industrial quantities: vehicles, cargo, and agricultural yields. One metric tonne equals exactly 1,000 kg.

Imperial/customary system:

Ounces are used in the US for smaller weights in cooking, postal parcels, and products. One ounce = 28.3495 grams, and 16 ounces make one pound. Pounds are the primary everyday weight unit in the US — body weight, grocery packaging, and vehicle payloads. One pound = 453.592 grams. Stone is used almost exclusively in the UK and Ireland for body weight. One stone = 14 pounds = 6.350 kg.

How the Conversion Works

The calculator converts everything through a gram-based reference:

1. Convert the input value to grams by multiplying by that unit's gram-equivalent.
2. Convert the gram total to the target unit by dividing by its gram-equivalent.

For example, converting 75 kg to pounds:

• 75 kg × 1,000 = 75,000 grams
• 75,000 / 453.59237 = 165.347 lb

This two-step method works for any pair of units without needing a separate conversion factor for every possible combination.

A Second Worked Example (8 Stone to Kilograms and Pounds)

UK body-weight figures are usually given in stone, which many US and metric readers find unfamiliar. Converting 8 stone:

1. Convert to grams: 8 × 6,350.29318 = 50,802.345 g
2. Convert to kilograms: 50,802.345 / 1,000 = 50.802 kg
3. Convert to pounds: 50,802.345 / 453.59237 = 112.0 lb

Verification Result: 8 stone = 50.802 kg = 112.0 lb. This comes out to an exact 112 lb because a stone is defined as exactly 14 pounds (8 × 14 = 112), unlike the kilogram figure, which involves a repeating decimal.

Key Conversion Reference

• 1 kg = 2.204623 lb
• 1 lb = 0.453592 kg
• 1 kg = 1,000 g
• 1 lb = 16 oz
• 1 stone = 14 lb = 6.350 kg
• 1 tonne = 1,000 kg = 2,204.623 lb
• 1 oz = 28.3495 g

About Decimal Results

The converter displays results to up to 6 decimal places. This precision is useful for scientific and pharmaceutical work where small differences matter. For everyday purposes, rounding to 2 or 3 decimal places is perfectly adequate. Converting 75 kg to pounds gives 165.347 lb — for body weight purposes, 165.3 lb is just as useful.

Common Mistakes

Frequently Asked Questions (FAQ)

Q1: How many pounds are in a kilogram?

One kilogram equals exactly 2.20462262 pounds. For everyday use, 1 kg is approximately 2.205 lb. The conversion factor comes from the defined relationship: 1 pound = 0.45359237 kg (exact, by international definition since 1959).

Q2: What is a stone in weight?

A stone is a unit of weight used primarily in the United Kingdom and Ireland for body weight. One stone equals exactly 14 pounds, or approximately 6.350 kilograms. If someone says they weigh 12 stone 4, that means 12 × 14 + 4 = 172 pounds, or about 78 kg.

Q3: Are ounces for weight the same as fluid ounces?

No, they measure entirely different things. An ounce (oz) measures mass or weight — 1 oz = 28.3495 grams. A fluid ounce (fl oz) measures liquid volume — 1 US fl oz = 29.5735 ml. A container of water might hold 8 fluid ounces but weigh slightly more than 8 ounces due to the difference between water's weight and the measurement convention.

Q4: What is the difference between a metric tonne and a US short ton?

A metric tonne (t) = 1,000 kg = 2,204.62 lb. A US short ton = 2,000 lb = 907.185 kg. This converter uses metric tonnes. When you see tonne spelled with an "e", it almost always means the metric version.

Q5: How many grams are in an ounce?

One ounce equals exactly 28.349523125 grams. So 1 gram = 1/28.3495 = 0.035274 oz. For cooking, the often-cited approximation is 28 grams per ounce, which is close enough for most recipes.