Buoyant Force Calculator

Use this tool to calculate the buoyant force of any object submerged or floating in any fluid.

Buoyant force on the object195.78 Nthe weight of 20 litres of this fluid — Archimedes' principle

Gauge pressure at depth97.89 kPa97.89 kPa, 14.198 psi, 0.9661 atm

Absolute pressure199.215 kPaincluding 101.325 kPa of surface pressure

Pressure per metre of depth9.789 kPa9.789 kPa a metre

Depth that adds one atmosphere10.3509 mabout 10 m in fresh water

Fluid density998.2 kg/m³pressure depends only on depth, density and gravity — not on the shape or volume of the container

Mass of fluid displaced19.964 kg

Weight in air147.0998 N

Apparent weight submerged0 Nit floats — buoyancy exceeds the weight

Object density750 kg/m³75.14% of the fluid density, so it floats with that fraction submerged

Fraction submerged when floating75.14%exactly the density ratio — which is why about 90% of an iceberg is underwater

Freeboard volume4.973 litres above the surface

Force on a 1 m² surface at this depth97.89 kNgauge pressure — the atmosphere pushes on both sides of most structures, so gauge is usually the right figure for a load

The formula

P = ρgh; buoyant force = ρ_fluid g V_displaced

Shape does not matter, and the fraction is the density ratio

Hydrostatic pressure depends only on depth, density and gravity. A narrow tube and a wide reservoir filled to the same depth exert identical pressure at the bottom, which strikes almost everyone as wrong the first time — the container's shape and the volume of fluid are both irrelevant.

Archimedes' principle says the buoyant force equals the weight of fluid displaced. The elegant consequence is that a floating object sits with exactly its density ratio submerged: ice at about 917 kg/m³ in seawater at 1025 floats with 89% below the surface, which is the origin of the iceberg cliché and is a precise result rather than an approximation.

Note the distinction between gauge and absolute pressure. Gauge is measured relative to the surrounding atmosphere and is what matters for structural loads, since the atmosphere pushes on both sides. Absolute includes the atmosphere and is what matters for boiling, cavitation and gas laws. Confusing them is a one-atmosphere error — negligible at depth, fatal near vacuum.