Buoyancy Calculator
Enter a fluid density and a displaced volume to get the buoyant force in newtons — the upward push Archimedes' principle says any fluid exerts on a body that displaces it.
Use SI units
Density in kg/m³ and volume in m³ give the force in newtons — one litre is 0.001 m³, so divide a volume in litres by 1000 before you start.
What is buoyancy?
The upward push of a fluid
Buoyancy is the upward force a fluid exerts on any object that displaces it, and it is exactly what lets ships float and makes objects feel lighter underwater. This buoyancy calculator applies Archimedes' principle — the buoyant force equals the weight of the fluid pushed aside — to turn two measurements, the fluid density in kilograms per cubic metre and the displaced volume in cubic metres, into the upward force in newtons. It is the number behind whether a hull floats, how much lift a balloon gets from the air, and why a fully loaded ship sits lower in the water than an empty one.
Enter a fluid density in kg/m³ and a displaced volume in m³ to get the buoyant force in newtons instantly.
The buoyant force is the fluid density multiplied by the acceleration due to gravity and by the displaced volume.
F = ρ × g × VHere ρ is the fluid density, g is standard gravity (9.80665 m/s²), and V is the volume of fluid displaced. Notice that the object's own weight never enters the formula — only the fluid and the volume it pushes aside matter. Suppose one litre of fresh water is displaced: the density is 1000 kg/m³, the volume is 0.001 m³, and the force is 1000 × 9.80665 × 0.001 = 9.80665 N, the weight of exactly one kilogram of water. Use kilograms per cubic metre and cubic metres and the force comes back in newtons.
The formula is exact for a fluid at rest, but a few practical points are worth keeping in mind.
Static fluids, consistent units, and float-vs-sink
This calculator gives the static buoyant force from a uniform fluid at rest; it does not model fluid motion, surface tension, or the compression of gases with depth. It uses standard gravity (9.80665 m/s²), so results differ slightly off Earth or at high altitude. Keep units consistent — kilograms per cubic metre and cubic metres — or the newtons will be wrong: one litre is 0.001 m³. The buoyant force alone does not tell you whether an object floats; compare it with the object's own weight to decide.