About the Weight Converter
From cooking to fitness tracking to shipping, weight conversions between metric and imperial units come up constantly - and the numbers rarely round out cleanly. Our Weight Converter handles milligrams, grams, kilograms, metric tons, ounces, pounds, and stone.
How It Works
Like our other converters, this tool converts your input through a common base unit (kilograms) using precise standard conversion factors, ensuring accuracy whether you're converting between closely related units or very different ones, like ounces to metric tons.
Formula & Methodology
Weight (technically mass, in scientific terms) uses the same base-unit conversion approach as length: every supported unit has one fixed factor relative to kilograms, so converting between any two units is a multiply-then-divide operation through that shared reference point. The pound, historically, was actually defined in terms of the kilogram (the international pound is fixed at exactly 0.45359237 kg), which is why modern pound-to-kilogram conversions are exact rather than approximate, even though the two systems evolved independently.
Step-by-Step: Calculating It By Hand
- 1Find your starting unit's conversion factor relative to kilograms (for example, 1 pound = 0.453592 kg).
- 2Multiply your input value by that factor to get the value in kilograms.
- 3Find your target unit's conversion factor relative to kilograms.
- 4Divide the value in kilograms by the target factor to get your final result.
Examples
Pounds to kilograms
160 lb converts to approximately 72.6 kg - a common conversion for body weight.
Grams to ounces
500 grams converts to approximately 17.6 ounces, useful for cooking measurements.
Advantages
- Covers the full range from milligrams to metric tons
- Includes stone, commonly used for body weight in the UK
- Precise conversion factors avoid compounding rounding errors
- Instant, no-signup conversion for quick everyday use
Common Mistakes
- Confusing a US ton (short ton) with a metric tonne - they aren't the same
- Mixing up mass (weight) with volume when converting cooking ingredients
- Rounding intermediate results before finishing a multi-step conversion
- Assuming 'stone' converts the same way across all English-speaking countries
Edge Cases to Watch For
- A US (short) ton is 2,000 pounds, while a metric tonne is 1,000 kilograms (about 2,204.6 pounds) and a UK (long) ton is 2,240 pounds - all three are different and easy to mix up.
- Stone (14 pounds) is used for body weight primarily in the UK and Ireland and rarely appears outside that context.
- Precision matters more at small scales - milligram-level conversions common in medicine or chemistry require carrying more decimal places than everyday kitchen conversions.
- Weight and mass are technically different physics concepts (mass is constant, weight depends on gravity), though this distinction essentially never matters for everyday unit conversion on Earth.
Common Use Cases
- Tracking body weight across different regional units
- Cooking and baking measurement conversions
- Shipping and freight weight calculations
- Academic, scientific, or engineering conversions