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Weight converter

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Ounces are avoirdupois, not troy or fluid ounces. Decimals: 12.5 or 12,5, without thousands separators.

How weight conversion works

Enter a value, select its current unit and choose the unit you need. The tool converts mass through kilograms using exact factors. Swap exchanges the units while keeping your entered number.

Kilograms, grams and metric prefixes

A kilogram contains 1000 grams. A gram contains 1000 milligrams, and a milligram contains 1000 micrograms. These conversions are exact powers of ten.

Converted value = Value × Source factor ÷ Target factor

  1. Choose the unit of your entered number.
  2. Select the destination unit.
  3. Read the instant result or copy it.

2.5 kg = 2500 g. A 500 mg quantity is 0.5 g.

Pounds, ounces, stone and tons

The international avoirdupois pound is exactly 0.45359237 kg. An ordinary ounce is 1/16 pound and a stone is 14 pounds. The metric tonne, US short ton and UK long ton are different units.

1 t = 1000 kg; 1 US ton = 2000 lb; 1 UK ton = 2240 lb

  1. Use Ounce for an ordinary mass ounce, not a troy ounce or fluid ounce.
  2. Select the named ton rather than assuming all tons are equal.
  3. Use Carat for gem mass: 1 ct = 0.2 g, not gold purity.

16 oz = 1 lb = 0.45359237 kg. One stone is 6.35029318 kg.

Rounding and the meaning of weight

In everyday use, weight often means mass. This tool converts mass units; it does not calculate gravitational force. Options sets the maximum decimal places, and ≈ marks a rounded answer. Signed values are accepted for mass changes.

1 µg = 0.000000000001 t

  1. Increase precision for very small quantities.
  2. Enter decimals rather than fractions such as 1/2.
  3. Copy uses the displayed precision; no extra digits are implied.

1 kg is approximately 2.204623 lb at six decimal places. At twelve decimal places, 1 µg in tonnes displays 0.000000000001.

Definitions: NIST mass factors and exact pound definition (note 22)