Buoyancy Calculator
Calculate buoyancy instantly in your browser — the published formula, worked locally with no data sent anywhere.
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What this tool does
Calculate buoyancy instantly in your browser — the published formula, worked locally with no data sent anywhere. Uses weight density (which already includes g), so the entered volume must be the submerged part. Surface tension and trapped air pockets are ignored.
How to use the Buoyancy Calculator
- Enter or select displaced / submerged volume in cuft.
- Enter or select fluid weight density (lb/cu ft — fresh water 62.4, seawater 64.0).
- Enter or select object average density (lb/cu ft, for the floating check).
- Read the calculated result; change any measurement to compare alternatives.
Formula
Archimedes' principle: buoyant force = weight of displaced fluid = fluid weight density × displaced volume. A floating object submerges the fraction (object density ÷ fluid density) of its volume.
- volume
- Displaced / submerged volume (cuft, before metric conversion)
- fluid
- Fluid weight density (lb/cu ft — fresh water 62.4, seawater 64.0)
- objDens
- Object average density (lb/cu ft, for the floating check)
Uses weight density (which already includes g), so the entered volume must be the submerged part. Surface tension and trapped air pockets are ignored.
Worked example
For buoyancy calculator, the following measurements illustrate the exact method: Displaced / submerged volume: 1; Fluid weight density (lb/cu ft — fresh water 62.4, seawater 64.0): 62.4; Object average density (lb/cu ft, for the floating check): 31.2.
Inputs
- Displaced / submerged volume1 cuft
- Fluid weight density (lb/cu ft — fresh water 62.4, seawater 64.0)62.4
- Object average density (lb/cu ft, for the floating check)31.2
Result
- Buoyant force (lbf)62.4
- Buoyant force (N)277.57
- Weight of displaced fluid (lb)62.4
- Floating behaviourFloats with 50.0% submerged
- Fraction submerged when floating0.5
Results explained
- Buoyant force (lbf)
- Buoyant force (lbf) from the formula above. Uses weight density (which already includes g), so the entered volume must be the submerged part. Surface tension and trapped air pockets are ignored.
- Buoyant force (N)
- Buoyant force (N) from the formula above. Uses weight density (which already includes g), so the entered volume must be the submerged part. Surface tension and trapped air pockets are ignored.
- Weight of displaced fluid (lb)
- Weight of displaced fluid (lb) from the formula above. Uses weight density (which already includes g), so the entered volume must be the submerged part. Surface tension and trapped air pockets are ignored.
- Floating behaviour
- Floating behaviour from the formula above. Uses weight density (which already includes g), so the entered volume must be the submerged part. Surface tension and trapped air pockets are ignored.
- Fraction submerged when floating
- Fraction submerged when floating from the formula above. Uses weight density (which already includes g), so the entered volume must be the submerged part. Surface tension and trapped air pockets are ignored.
Frequently asked questions
Archimedes' principle: buoyant force = weight of displaced fluid = fluid weight density × displaced volume. A floating object submerges the fraction (object density ÷ fluid density) of its volume.
Uses weight density (which already includes g), so the entered volume must be the submerged part. Surface tension and trapped air pockets are ignored.
Every field is labelled with its unit — enter values in exactly the labelled unit and read the result in the labelled output unit. Fields with a unit symbol also support the site-wide imperial/metric switch, which converts before the formula runs.
It uses double-precision arithmetic and the published constants and formulas named on this page. The last displayed digit may be rounded, and real conditions can differ from the idealized model described in the assumptions.
Yes. Every calculation runs entirely in your browser; nothing you enter is uploaded, stored or shared.