Weight Converter

About the Weight Converter

Convert between all common weight and mass units with this universal tool. Supports pounds, kilograms, ounces, grams, milligrams, stones, and metric tonnes with bidirectional conversion.

Weight conversion is needed daily across cooking, fitness tracking, shipping, science, and international commerce. The US and UK use pounds and ounces for most everyday purposes, while the rest of the world uses kilograms and grams. Health and fitness contexts often require conversion between these systems.

All conversion factors used are internationally standardized. The pound (avoirdupois) is defined as exactly 0.45359237 kilograms, and all other relationships derive from this.

When This Page Helps

A single tool for all weight conversions saves time and prevents errors from using approximate factors. Shipping, cooking, fitness, and scientific applications all need precise weight conversion.

How to Use the Inputs

1. Select the unit you are converting from.
2. Select the unit you are converting to.
3. Enter the value to convert.
4. The result appears in the output panel.
5. Use the conversion factor display to verify the math.

Example Calculation

Tips & Best Practices

• Quick lb to kg: divide pounds by 2.2 for a close estimate.
• One kilogram is about 2.205 pounds.
• Stone is commonly used in the UK for body weight: 1 stone = 14 pounds.
• Metric tonnes (1,000 kg) differ from US short tons (2,000 lb = 907.2 kg) and long tons (2,240 lb = 1,016 kg).
• For cooking, grams are more precise than ounces for small measurements.

Weight Measurement Systems

The avoirdupois system (pounds, ounces) is the most common weight system in the US and UK for everyday use. The metric system (grams, kilograms) is used internationally and in all scientific contexts. The troy system (troy ounces, troy pounds) is used exclusively for precious metals.

Historical Context

The pound was historically defined by a physical artifact. In 1959, the international yard and pound agreement defined the pound as exactly 0.45359237 kilograms, linking the imperial and metric systems with mathematical precision.

Body Weight Conversion

Body weight is perhaps the most personal weight conversion people need. Americans think in pounds, the British often use stone, and the rest of the world uses kilograms. Fitness apps and medical records may require any of these units.

Frequently Asked Questions

• How many kilograms in a pound?

  One pound equals 0.453592 kilograms (exactly 0.45359237 kg). This is an internationally defined constant. To convert pounds to kg, multiply by 0.453592.

• How many ounces in a pound?

  There are 16 avoirdupois ounces in one pound. This is the standard "ounce" used for everyday weight measurement. Troy ounces (used for precious metals) are different: 12 troy ounces per troy pound.

• What is a stone in pounds?

  One stone equals exactly 14 pounds, or approximately 6.35 kilograms. Stone is commonly used in the UK and Ireland for body weight. A person weighing 160 lb is 11 stone 6 pounds.

• What is the difference between mass and weight?

  Mass is the amount of matter (measured in kg/lb) and is constant everywhere. Weight is the force of gravity on that mass and varies by location. On Earth's surface, the distinction is negligible for everyday purposes, and the terms are used interchangeably.

• How do I convert grams to ounces?

  Divide grams by 28.3495 to get ounces. For example, 100 g / 28.3495 = 3.527 oz. Conversely, multiply ounces by 28.3495 to get grams.

• What is a metric tonne?

  A metric tonne (or "tonne") equals 1,000 kilograms or approximately 2,204.6 pounds. It differs from a US short ton (2,000 lb) and a British long ton (2,240 lb). Metric tonnes are the international standard for large-scale weight measurement.