Buoyancy is why boats float, balloons rise and you feel lighter in a pool. The upward force equals the weight of the displaced fluid.
How to use the Buoyancy Calculator
- Fluid
- Fluid density ρ
- Submerged volume V
- Gravitational acceleration g
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the fluid (or enter its density), enter the submerged volume and the gravitational acceleration.
Inputs explained
| Field | What to enter |
|---|---|
| Fluid | Choose one: Fresh water (20 °C), Seawater, Air (sea level, 15 °C), Ethanol … |
| Fluid density ρ | Units: kg/m³, g/cm³, g/mL, lb/ft³, lb/in³ |
| Submerged volume V | Units: L, mL, m³, US gal, ft³ |
| Gravitational acceleration g | Units: m/s², ft/s², g, cm/s² |
What each result means
- Buoyant force F_B = [rho]×[Submerged volume V]×[Gravitational acceleration g]
- Displaced fluid mass = [rho]×[Submerged volume V]
- Mass that can be supported = [rho]×[Submerged volume V]
Example values
How the main result changes when Fluid density ρ changes and everything else stays at the example values above:
| Fluid density ρ (kg/m³) | Buoyant force F_B (N) |
|---|---|
| 500 | 97.89 |
| 750 | 97.89 |
| 1,000 | 97.89 |
| 1,250 | 97.89 |
| 1,500 | 97.89 |
| 2,000 | 97.89 |
Formula
F_B = ρ·V·g
Worked example
Inputs: Fluid: Fresh water (20 °C); Submerged volume V: 10 L; Gravitational acceleration g: 9.80665 m/s².
Results: Buoyant force F_B = 97.88998 N; Displaced fluid mass = 9.982 kg; Mass that can be supported = 9.982 kg.
Key terms
- Displacement
- Volume of fluid pushed aside by an object.
Frequently asked questions
Does buoyancy depend on the object's weight?
No, only on the displaced volume and fluid density.
Why is it easier to float in the sea?
Seawater is denser than fresh water.
Does buoyancy work in air?
Yes, that's how balloons fly.
What about on the Moon?
Buoyancy is smaller because g is smaller, but so is weight.