Weight Converter

How to use this Weight Converter

What this calculator does

This calculator converts a mass from one supported unit to another and simultaneously shows the same mass in a broader conversion table. In everyday speech, people often say “weight” when they mean mass; technically, weight is a force while mass is the quantity measured in kilograms, pounds, ounces, and the other units used here. The calculator therefore performs mass-unit conversions. For the scientific distinction and the modern SI definition of mass, see NIST's SI Units – Mass guidance.

When to use it

Use the converter when you need to translate a product specification from kilograms to pounds, compare a laboratory value expressed in grams with an ounce-based value, translate stone measurements into metric units, or inspect very small atomic-scale and very large astronomical-scale mass equivalents. It is a unit converter, not a density calculator: converting between mass and volume, such as grams and cups, requires information about the material's density and is outside this tool's scope.

How to calculate

1. The calculator opens with a ready-to-use example of 70 kilograms converted to pounds, and the example Excel workbook is immediately available.
2. Replace Amount with your value. You can use a plain decimal, correctly grouped U.S. thousands such as 12,500.5, or scientific notation such as 1.2e-6.
3. Choose From unit. If you change this unit after entering a valid amount, the amount itself is converted so the underlying mass remains unchanged.
4. Choose To unit to select the unit shown as the primary Converted amount. Read the Base mass, Conversion factor, summary pills, and the complete Conversion table for equivalent values.
5. Select Download Excel to export the current validated model as an XLSX workbook. Reset clears the demonstration amount and calculated content; after Reset, Excel export is disabled until you enter a complete valid amount again.

Input guide

Amount is required and must be a finite, non-negative number no larger than 1e200. The accepted convention uses a decimal point; a comma is accepted only as a correctly placed thousands separator, so “1,5” is rejected rather than silently interpreted as 15. Example: 70. Increasing Amount increases every equivalent value proportionally. From unit is required and identifies the unit attached to Amount; example: Kilogram (kg). A common mistake is changing the unit label without converting the number, so this interface preserves the same mass automatically when the From unit changes. To unit is required and selects the primary output unit; example: Pound (lb). Changing it does not change the underlying mass, only the highlighted representation.

Output guide

Converted amount is the exact conversion identity evaluated from the current Amount and unit pair, displayed with adaptive precision. Base mass is the same value expressed in kilograms, the SI base unit of mass. Conversion factor reports how many target units correspond to one source unit. The live summary pills labeled kg, g, oz, and st provide quick common-unit checks. The Conversion table lists Unit, Symbol, and Equivalent amount for every supported metric, Imperial/US, troy, atomic, particle-rest-mass, and astronomical unit. A zero input produces zero in every row; extremely small or large equivalents use scientific notation so magnitude is preserved.

Worked example

The startup example uses 70 kg. The international avoirdupois pound is exactly 0.45359237 kg, so the conversion is 70 kg ÷ 0.45359237 kg/lb = 154.323583529... lb. The calculator displays this as 154.323584 lb. The same canonical mass also gives about 2,469.177 oz and 11.023113 st. NIST's official conversion-factor tables document the pound and avoirdupois ounce relationships used for these conversions.

Learn more

The kilogram is the SI base unit for mass and is now defined through a fixed value of the Planck constant rather than a physical artifact. NIST's definitions of the SI base units explain that modern definition and place the kilogram alongside the other six SI base units.