KEVOS® MAKEOS · Hydraulics

Buoyancy and Submerged Weight

Will this body float, and how much does it weigh when submerged?

Buoyant force by Archimedes’ principle, the apparent (submerged) weight of a body, whether it floats, and the fraction of its volume below the surface when it does.

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How this tool works

Inputs, units and where to find them

InputUnitTypical source
Volume of the bodyLTotal external volume of the body (displacement when fully submerged).
Mass of the bodykgMass of the body.
Fluid densitykg/m³Density of the fluid (fresh water about 1000, sea water about 1025 kg/m³).

Method and formulas

  1. Buoyant force = ρ g V (weight of fluid displaced).
  2. Apparent weight = m g − ρ g V.
  3. A body less dense than the fluid floats with ρ_body ÷ ρ_fluid of its volume submerged.
  4. Example: 10 L at 78.5 kg has a buoyant force of 98.067 N in 1000 kg/m³ fluid.

Limitations

  • Static fluid; flow, waves and lift from motion are excluded.
  • Floating stability (metacentric height) is not checked.
  • Example values are illustrations. Replace them with values for your actual task.

Typical uses

  • Find the lifting force needed for a part underwater
  • Check whether a float or tank will float and how deep
  • Size ballast for a submerged structure

Who it is for

  • Design engineers
  • Rigging supervisors
  • Process engineers

What you get

  • Buoyant force when fully submerged
  • Apparent weight in the fluid
  • Floating draught fraction

Interpreting the result

  • When lifting a submerged load, the crane takes the full weight as the load clears the surface.

References

  • Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3027. Topic reference; no source tables or recommended settings are reproduced.

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Open the Buoyancy and Submerged Weight calculator