Archimedes' Principle

A buoyancy calculator applies Archimedes' principle: the upward buoyant force on a submerged object equals the weight of the fluid it displaces. The formula is Fb = ρ × V × g, where ρ is fluid density, V is displaced volume, and g is gravitational acceleration (9.81 m/s²).

Floating vs Sinking

Whether an object floats depends on density, not size. If the object's density is below the fluid's density, the buoyant force at full submersion exceeds the object's weight, so it rises until only part of it is submerged — the fraction submerged equals the density ratio. If the object is denser than the fluid, it sinks.

Everyday Buoyancy

Ice floats because its density (917 kg/m³) is below water's. Ships float by displacing enough water to match their total weight. Hot air balloons use the same principle in air, and submarines control their average density with ballast tanks. The net force this calculator reports tells you whether an object will rise, sink, or hover.