Weight & Mass Converter
This converter uses the exact defined pound–kilogram relationship (1 lb = 0.45359237 kg) and standard metric relationships and is reviewed for calculation accuracy and clarity. Results are rounded for display where appropriate.
Convert between kilograms, pounds, grams, ounces, milligrams, metric tons, and US tons in any direction. Enter a value, choose the source and target unit, and the tool returns the converted result, the same amount expressed in every supported unit, the exact conversion factor, the substituted equation, and a reference table for common weights.
Example result shown below. Edit the fields above and it recalculates instantly.
How It Works
Mass conversions are purely proportional: every unit is a fixed multiple of a base unit (here, the gram), so converting is a single multiplication or division by an exact factor. The pound is defined as exactly 0.45359237 kilograms, and the ounce is exactly 1/16 of a pound, so these are not approximations — they are exact by international agreement, and any rounding you see is only in the display.
Metric units scale by powers of ten (1 kg = 1,000 g = 1,000,000 mg; 1 metric ton = 1,000 kg). The customary units — ounces, pounds, US tons — relate to the metric base through the pound definition.
Worked Examples
Kilograms to pounds: 1 kg ≈ 2.204623 lb; 100 kg ≈ 220.4623 lb.
Pounds to kilograms: 1 lb ≈ 0.453592 kg; 150 lb ≈ 68.0389 kg.
Grams and ounces: 100 g ≈ 3.5274 oz; 1 oz = 28.349523 g.
Tons: 1 metric ton = 1,000 kg ≈ 2,204.62 lb; 1 US ton = 2,000 lb ≈ 907.18 kg.
What This Result Means
The headline is your direct conversion; the "All units" table shows the same mass in every supported unit at once, which is handy when a spec lists one unit and you think in another. Note that "weight" in everyday use is really mass here — the converter does not model gravity or force.
When to Use This Calculator
Use it for shipping and luggage limits, recipes and food labels that mix metric and customary units, body weight, gym and freight figures, and lab or product specs that need grams or milligrams.
Limitations
- Negative mass is not physically meaningful, so negative inputs are rejected with a clear message.
- These are mass units, not force; the tool does not convert to newtons or account for gravity.
- Results are displayed to a sensible precision while the exact pound definition (0.45359237 kg) is used internally.
Frequently Asked Questions
How many pounds are in a kilogram?
One kilogram is about 2.2046226 pounds. Equivalently, one pound is exactly 0.45359237 kilograms.
Is a US ton the same as a metric ton?
No. A US (short) ton is 2,000 pounds ≈ 907.18 kg. A metric ton (tonne) is 1,000 kg ≈ 2,204.62 lb — about 10% heavier.
How many grams in an ounce?
Exactly 28.349523125 grams, because an ounce is defined as 1/16 of the 0.45359237 kg pound.
Is this weight or mass?
Mass. In everyday language people say "weight," but these units (kg, lb, g) measure mass. True weight is a force and depends on gravity, which this tool does not model.