Buoyant Force Calculator

How it is calculated

The tool uses Archimedes' principle: the upward force equals the weight of the fluid displaced. First the displaced mass m = ρ × V, then the force F = m × g. Here ρ is the fluid density in kg/m³, V is the displaced volume in m³ (the submerged part of the object, not the whole object if it floats), g is gravitational acceleration in m/s², and F comes out in newtons.

Only the volume is required and it must be greater than zero. If the density is left empty or is zero or negative, the tool assumes 1000 kg/m³ (fresh water); if g is empty or not positive, it uses 9.81 m/s². The tool does not compare the force with the object's weight, so you need to do that yourself to know whether the object floats.

Common mistakes

• Entering the volume of the whole object for a floating body; only the part below the waterline displaces fluid.
• Using litres or cubic centimetres for the volume; the tool expects m³, so 500 litres must be typed as 0.5.
• Leaving the density empty for salt water or oil and not noticing that the tool silently used 1000 kg/m³.
• Entering density in g/cm³ (1.025) instead of kg/m³ (1025); the force then comes out 1000 times too small.
• Treating the buoyant force as the object's weight; the object floats only if its own weight is no more than this force.