Buoyancy Force Calculator Formula
Understand the math behind the buoyancy force calculator. Each variable explained with a worked example.
Formulas Used
Buoyant Force
buoyancy = fluid_density * 9.81 * volumeEquivalent Mass Supported
buoyancy_kg = fluid_density * volumeVariables
| Variable | Description | Default |
|---|---|---|
fluid_density | Fluid Density (rho)(kg/m^3) | 1000 |
volume | Submerged Volume (V)(m^3) | 0.05 |
How It Works
Archimedes' Principle
Any body submerged in a fluid experiences an upward buoyant force equal to the weight of the displaced fluid.
Formula
F_b = rho_fluid x g x V_displaced
where rho_fluid is the fluid density, g = 9.81 m/s^2, and V_displaced is the volume of fluid pushed aside by the object. An object floats when the buoyant force equals its weight.
Worked Example
A 0.05 m^3 object fully submerged in water (1000 kg/m^3).
- 01F_b = 1000 x 9.81 x 0.05 = 490.5 N
- 02Equivalent mass = 1000 x 0.05 = 50 kg
- 03If the object weighs less than 490.5 N, it will float.
Frequently Asked Questions
How do I find the submerged volume?
For a fully submerged object, use its total volume. For a floating object, the submerged volume is the portion below the waterline, which can be calculated from the weight: V_submerged = m_object / rho_fluid.
Does shape affect buoyancy?
No. Buoyancy depends only on the displaced volume and fluid density, not on the shape of the object. A sphere and a cube of the same volume experience the same buoyant force.
What is the density of seawater?
Seawater has a density of approximately 1025 kg/m^3, about 2.5% denser than fresh water. This means objects are slightly more buoyant in seawater.
Ready to run the numbers?
Open Buoyancy Force Calculator