The buoyancy calculator computes buoyant force using Archimedes' principle: F = ρ_fluid × V_submerged × g. Enter the fluid density, submerged volume, and object weight to determine buoyant force and whether the object floats or sinks.
Buoyancy Calculator
How to Use the Buoyancy Calculator
Archimedes' principle: any object submerged in a fluid experiences an upward buoyant force equal to the weight of fluid displaced. If this force exceeds the object's weight, it floats.
Step 1: Enter Fluid Density
Use a preset (fresh water 1000 kg/m³, sea water 1025 kg/m³, oil ~800 kg/m³) or enter any custom density.
Step 2: Enter Submerged Volume
Enter the volume of the object that is submerged. For full submersion, this equals the object's total volume.
Float/Sink Determination
If you enter object weight, the calculator compares it to buoyant force. If F_buoyancy > Weight, the object floats. If equal, it's neutrally buoyant. If less, it sinks.
Example
A 0.001 m³ (1 liter) aluminum block (mass 2.7 kg, weight 26.5 N) in fresh water: Buoyant force = 1000 × 0.001 × 9.81 = 9.81 N. Since 9.81 N < 26.5 N, it sinks.
FAQ
What is Archimedes' principle?
Archimedes' principle states that any object submerged in a fluid experiences an upward buoyant force equal to the weight of fluid displaced. Buoyant force F = ρ_fluid × V_submerged × g. If the buoyant force equals the object's weight, it floats. If less, it sinks.
Why does steel float when shaped into a ship?
Steel itself sinks (density ~7,800 kg/m³). But a ship-shaped hull traps large amounts of air, reducing the average density of the entire vessel below water's 1,000 kg/m³. The ship displaces water weighing more than the ship itself, so it floats.
Is this calculator free?
Yes, completely free with no signup required. All calculations run in your browser.
Is my data private?
Yes. All calculations run locally. Nothing is transmitted.
What is the buoyancy of an object in seawater vs fresh water?
Seawater is about 2.5% denser than fresh water (~1025 vs 1000 kg/m³), so buoyant force is about 2.5% greater in seawater. This is why objects are slightly more buoyant in the ocean — you float higher and feel lighter in salt water than in a freshwater pool.