Weight Calculator

What this calculator does

The Weight Calculator has two modes. The first calculates the force of gravity on an object using weight = mass × gravity. It reports the result in newtons and also shows kilogram-force and pound-force. The second mode converts a value between common mass units, including kilograms, grams, milligrams, metric tons, pounds, ounces, carats, atomic mass units, grains, quarters, and stones.

Mass is the amount of matter in an object and does not change on another planet. Weight is the gravitational force on that mass and depends on local gravity. In everyday speech, people often say "weight" when they mean mass, which is why the converter mode is included.

How to use this calculator

For the physics calculation:

1. Choose "Find weight (m × g)".
2. Enter the mass and select its unit.
3. Choose a gravity preset, such as Earth, Moon, or Mars.
4. Click Calculate.

For a unit conversion:

1. Choose "Convert mass units".
2. Enter the value.
3. Select the unit to convert from and the unit to convert to.
4. Click Calculate.

The default weight example uses 70 kilograms on Earth, where gravity is 9.80665 m/s². The result is 686.4655 newtons, which is exactly 70 kilogram-force, or about 154.32 pound-force. The default conversion example converts 1 pound to 0.45359237 kilograms.

Formulas

Weight from mass:

W = m × g

W is weight in newtons, m is mass in kilograms, and g is gravitational acceleration in meters per second squared. Kilogram-force is the weight divided by 9.80665, and pound-force is the weight divided by 4.4482216152605.

Mass unit conversion:

result = value × factor(from unit) ÷ factor(to unit)

Each unit is expressed in kilograms for the conversion. For example, 1 pound is 0.45359237 kilograms, 1 ounce is 0.028349523125 kilograms, and 1 metric ton is 1,000 kilograms.

What the results mean

In weight mode, the headline figure is the force in newtons. The summary rows show the mass, gravitational acceleration, and equivalent values in kilogram-force and pound-force. A 70-kilogram person weighs about 686 newtons on Earth, 113 newtons on the Moon, and 260 newtons on Mars.

In conversion mode, the headline shows the input and output with unit symbols. The summary also shows the value in kilograms, the common base for all supported mass units.

Assumptions and limitations

• Weight uses a constant gravitational acceleration. The calculator does not model altitude, latitude, Earth's rotation, or local anomalies.
• Gravity presets are approximate average surface values.
• The conversion mode converts mass, not force units such as newtons, pound-force, or dyne.
• The metric ton is 1,000 kilograms, not the US short ton or UK long ton.
• The calculator ignores buoyancy, which can slightly reduce measured weight in air or water.
• Negative mass is rejected. Zero mass is allowed and produces zero weight.
• Results are rounded. Pound-force uses standard gravity of 9.80665 m/s².

Frequently asked questions

What is the difference between weight and mass?

Mass is a measure of how much matter an object contains and is measured in kilograms. Weight is the gravitational force on that mass and is measured in newtons. A 70-kilogram person has the same mass everywhere but a different weight on the Moon.

How much does 70 kilograms weigh on Earth?

Using standard gravity of 9.80665 m/s², 70 kilograms weighs 686.4655 newtons. That is 70 kilogram-force or about 154.32 pound-force.

Why does the converter say 1 pound equals 0.45359237 kilograms?

That is the exact definition of the international avoirdupois pound, agreed upon in 1959. The value is exact, not an approximation, although displayed results may be rounded.

Reference table

Celestial body masses

The calculator converts weight between units; the table gives mass references for very large objects. Weight depends on local gravity, while mass does not.

Source

Reference: Calculator.net — Weight Calculator. Standard gravity and mass-unit definitions can be verified with NIST and international measurement standards.

Disclaimer

This calculator is intended for education and everyday estimation. It is not a precision instrument for engineering, trade, or scientific measurement, and it does not account for local gravity or buoyancy effects.