Force Converter

Enter a force in any of the listed units — millinewton through meganewton, dyne, gram-force, kilogram-force, metric ton-force, ounce-force and pound-force — and every other one updates at once. The value is taken to newtons and back out again, so nothing accumulates rounding on the way through.

Half of those units are forces named after masses, and that is the source of most confusion in this table. A kilogram is an amount of matter; a kilogram-force is the weight of that matter in standard gravity, fixed by definition at exactly 9.80665 newtons. The same pairing gives pound-force, which is 4.44822 newtons. They are useful precisely because people think in terms of how heavy something is, and they are a trap in any calculation where mass and force both appear, because the number is the same and the quantity is not.

The constant in that definition is a convention, not a measurement of where you are standing. Actual gravity runs from about 9.780 m/s² at the equator to 9.832 at the poles, a spread of roughly half a percent from the Earth's rotation and its shape. A spring scale calibrated in kilogram-force in one city reads slightly differently in another, which is why laboratory balances are recalibrated after being moved and why trade-legal scales carry a gravity zone marking. A beam balance comparing two masses is immune, since gravity acts on both pans equally.

The imperial side has an extra trap worth naming. There are two mass units and two force units in that system, and they do not pair up the way the names suggest: the pound-mass goes with the poundal, and the pound-force goes with the slug. Mixing a pound-mass with a pound-force in Newton's second law introduces a factor of 32.174 that is easy to lose and produces answers wrong by that much. The dyne is a leftover from the CGS system, a hundred-thousandth of a newton, and still turns up in surface tension and older physics literature.