Archimedes' Principle Calculator

Frequently Asked Questions

What is Archimedes' principle?

The buoyant force on a submerged object equals the weight of fluid it displaces. Discovered by Archimedes ~250 BCE.

When does an object float?

When its average density is less than the fluid's density. The submerged fraction equals object density / fluid density.

What's apparent weight?

Weight minus buoyant force - what a scale reads when the object is submerged. A 100 N object losing 30 N of buoyancy weighs 70 N apparent.

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This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

Archimedes' principle: a body submerged in fluid feels an upward force equal to the weight of the displaced fluid. Enter the object's mass, volume, and the fluid density; the calculator reports object density, whether it floats or sinks, the buoyant force in either case, the submerged fraction (if floating), and the apparent weight you would feel if it were submerged.

Worked Example

A 10 kg block of volume 8 L (0.008 m³) in fresh water (1000 kg/m³). Density = 10 / 0.008 = 1250 kg/m³ (heavier than water), so it sinks. Max buoyant force = 1000 × 0.008 × 9.81 = 78.5 N. Object weight = 10 × 9.81 = 98.1 N. Apparent weight in water = 98.1 − 78.5 = 19.6 N - much lighter than in air.

Common Mistakes

Confusing volume units. Use liters; the calculator converts to m³ (1 L = 0.001 m³).

Using object weight (N) where mass (kg) is required - divide weight by g first.

Forgetting that apparent weight is what a fish-scale or hand actually feels - useful in shipbuilding, diving, and lab buoyancy corrections.

Confusing this with the Buoyancy calculator - this one asks for mass and volume of the object; the other asks for volume + fluid choice to give force.

Tips & FAQ

Why is the iceberg only partly visible? Ice SG ≈ 0.917, so about 92% sits underwater - the visible "tip" is the other 8%.

Apparent weight of a person in water? Average human density ~ 985 kg/m³ floats barely; salt water (1025) is more buoyant.

Lifting a sunken object? Apparent weight is the force needed to lift it underwater - much less than its full weight in air.

Archimedes' Principle Calculator

Frequently Asked Questions

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