What is Archimedes' principle?

Archimedes' principle states that any object fully or partially submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces. In formula form: F = ρ × g × V, where ρ is fluid density, g is gravitational acceleration, and V is the displaced volume.

What units does this calculator use?

In SI mode, density is in kg/m³, gravity in m/s², volume in m³, and force output is in Newtons (N). In Imperial mode, density is in lb/ft³, gravity in ft/s², volume in ft³, and force output is in pound-force (lbf).

What is the density of seawater vs. fresh water?

Fresh water has a density of approximately 1000 kg/m³ (62.4 lb/ft³). Seawater is denser at about 1025 kg/m³ (64.0 lb/ft³), which is why objects float more easily in the ocean than in a freshwater lake.

How do I know if an object will float?

An object floats when the buoyant force equals or exceeds its weight. If the average density of the object is less than the fluid density, it floats. Use the weight comparison section in this tool to check — enter the object's weight to see whether it sinks or floats.

Does buoyancy change with depth?

For incompressible fluids like water, the buoyant force depends only on the volume displaced and fluid density, not on the depth of submersion. However, for compressible objects or gases, increasing pressure at greater depths can reduce displaced volume and thus reduce buoyancy.

Buoyancy Calculator

Name: Buoyancy Calculator
Availability: InStock
Author: Nham Vu

Calculate the buoyant force on a submerged object by entering fluid density, gravity, and displaced volume.

Inputs

Unit System

Fluid Density (kg/m³)

Gravitational Acceleration (m/s²)

Displaced Volume (m³)

Object Weight (optional, for float/sink check) (N)

Enter values on the left and click Calculate to see the buoyant force.

Summary

Calculate the buoyant force on a submerged object by entering fluid density, gravity, and displaced volume.

How it works

Select your preferred unit system (SI or Imperial).
Enter the density of the fluid the object is submerged in.
Enter the gravitational acceleration (pre-filled with standard values).
Enter the volume of fluid displaced by the object.
The buoyant force F = ρ × g × V is calculated and displayed instantly.
Compare the buoyant force to the object's weight to determine if it floats.

Use cases

Determine whether a ship hull or vessel design will float.
Calculate the lift force on a submerged submarine ballast tank.
Solve physics homework problems involving Archimedes' principle.
Estimate the buoyancy of a floating dock or pontoon.
Verify hydrostatic calculations in fluid mechanics coursework.
Explore how fluid density affects buoyancy (e.g., seawater vs. fresh water).
Check if a sealed container will float in a given liquid.
Understand the upthrust on underwater structures like pipelines.

Frequently Asked Questions

Last updated: 2026-06-15 · Reviewed by Nham Vu