Calculates the upward buoyant force a fluid exerts on a submerged or partially submerged object, using Archimedes’ Principle.
How it works
The fluid’s density is multiplied by the volume of fluid displaced and by gravitational acceleration to give the buoyant force.
What this does not include
This does not include determining whether an object actually floats or sinks — that also depends on comparing this buoyant force to the object’s own weight, which isn’t part of this calculation.
How to use this calculator
- Enter the fluid’s density and the volume of fluid displaced.
A worked example
An object displacing 0.05 m³ of water (density 1000 kg/m³): buoyant force = ρ×V×g = 1000 × 0.05 × 9.80665 = 490.3325 N.
An object displacing 2 m³ of air (density 1.225 kg/m³): buoyant force = 24.0263 N — much smaller, since air is far less dense than water.
What the variables mean
| Variable | Meaning |
|---|---|
| Density | Density of the fluid being displaced |
| Volume | Volume of fluid displaced by the object |
Edge cases worth knowing
Buoyant force depends only on displaced fluid, not the object’s own weight or material — Archimedes’ principle, which is why identical-volume objects of very different materials experience identical buoyant force in the same fluid.
A negative fluid density has no physical meaning, so the calculator declines to show a result for that input.
Frequently asked questions
Why does a steel ship float if steel is denser than water?
Because the ship’s hull shape displaces a large volume of water, creating enough buoyant force to support the ship’s total weight — the shape matters, not just the material.
What determines whether an object floats or sinks?
An object floats if the buoyant force from its displaced fluid equals or exceeds its own weight — otherwise it sinks.
Does buoyant force depend on how deep an object is submerged?
Only through the volume of fluid displaced — a fully submerged object displaces the same volume (and feels the same buoyant force) regardless of depth, assuming the fluid’s density doesn’t change.
