Enter Object Information
Provide the object's mass and the volume of fluid it displaces. Select the appropriate units for each value.
Buoyancy Calculator
Calculate buoyant force using Archimedes' principle and determine whether an object will float, sink, or remain neutrally buoyant in a selected fluid.
Calculate Buoyant Force
Enter the object's mass, displaced volume, and fluid properties.
Buoyant force
0 N
Object weight
0 N
Net vertical force
0 N
Apparent weight
0 N
| Fluid density | 0 kg/m³ |
|---|---|
| Displaced volume | 0 m³ |
| Mass of displaced fluid | 0 kg |
| Object average density | Available in full-volume mode |
| Relative density | Available in full-volume mode |
| Estimated submerged percentage | Available in full-volume mode |
| Force direction | Not calculated |
What Is a Buoyancy Calculator?
A buoyancy calculator determines the upward force that a fluid applies to a partially or completely submerged object. This force is called the buoyant force or upthrust.
The calculator compares buoyant force with the object's gravitational weight. That comparison helps determine whether the object has an upward tendency, a downward tendency, or neutral buoyancy.
Archimedes' Principle
Archimedes' principle states that the buoyant force acting on an object equals the weight of the fluid displaced by that object. The principle applies to liquids and gases.
Fb = ρ × g × V
Buoyant force = fluid density × gravitational acceleration ×
displaced volume
- Fb is buoyant force in newtons.
- ρ is fluid density in kilograms per cubic meter.
- g is gravitational acceleration in meters per second squared.
- V is displaced fluid volume in cubic meters.
How the Buoyancy Calculator Works
Select the Fluid
Choose water, seawater, oil, ethanol, air, or another preset. You can also enter a custom fluid density.
Review the Results
The tool calculates buoyant force, object weight, apparent weight, net force, and the expected floating condition.
Understanding Float, Sink, and Neutral Buoyancy
Object Floats or Accelerates Upward
When the maximum available buoyant force is greater than the object's weight, the object has an upward tendency. A freely floating object rises until it displaces only enough fluid for buoyant force to equal its weight.
Object Sinks
An object sinks when its weight is greater than the buoyant force produced by the displaced fluid. This commonly occurs when the object's average density is greater than the fluid density.
Neutral Buoyancy
Neutral buoyancy occurs when buoyant force and object weight are approximately equal. The object can remain suspended at a stable depth when other forces are negligible.
Real-world motion may also be affected by drag, surface
tension, trapped air, fluid movement, object shape, pressure,
and contact with a container.
Practical Uses of Buoyancy Calculations
Buoyancy calculations are useful in marine engineering, shipbuilding, underwater robotics, diving, aviation, fluid mechanics, material testing, and classroom physics.
- Estimating whether a boat or floating platform can stay afloat.
- Calculating lift for underwater equipment and remotely operated vehicles.
- Choosing ballast for submarines, diving systems, and research instruments.
- Comparing the behavior of an object in fresh water and seawater.
- Estimating the apparent weight of a submerged object.
- Teaching Archimedes' principle and density relationships.
Frequently Asked Questions
Buoyant force is the upward force exerted by a fluid on an object that is partially or fully immersed in that fluid. Its magnitude equals the weight of the displaced fluid.
Multiply the fluid density by gravitational acceleration and the displaced fluid volume. In SI units, the result is expressed in newtons.
No. An object's total mass alone does not determine whether it sinks. Its average density, shape, displaced volume, and the density of the surrounding fluid are also important.
Seawater is denser than fresh water. The same displaced volume therefore has more mass and weight, producing a greater buoyant force.
Apparent weight is the object's gravitational weight minus the buoyant force acting on it. A negative result indicates that the upward buoyant force exceeds the object's weight.
Yes. Air is a fluid and produces buoyancy. Select the air density preset or enter a custom density based on the temperature, pressure, and altitude.
Enter the actual volume below the fluid surface. For a completely submerged object, this usually equals the full external object volume. For a floating object, only part of its volume is submerged.