How do you calculate the force of buoyancy?

`F_b=rhogV`

Where,

`F_b` is the buoyant force
`rho` is the density of the fluid
`g` is the acceleration due to gravity (`~~9.81ms^-2`)
`V` is the volume of the fluid the object emerges in.

The buoyancy force is the upward force acting on an object that is caused by a displaced fluid. The more fluid that's displaced, the greater the buoyant force is.

If an object is fully submerged in the fluid, it experiences the maximum buoyant force. This also results in an increase in pressure.

`Pressure = (mass)/(Volume)` (Pa)

So if the pressure increases, then the volume would decrease as the volume is inversely proportional to the pressure.

If `V` is the volume of a solid body submerged in the fluid of density `\rho` then the buoyant force `F_B` acting on the body will be equal to the weight of fluid displaced by the body which is partially or fully submerged into the fluid.

The buoyant force `F_B` is given as

`F_B=\text{weight of fluid of volume V & density}\ rho`

`=\rho V g`

Other answers focused on a submerged object. For a floating object, the `"force of buoyancy" = "its weight"`.

I hope this helps,
Steve