In a situation of fluid statics, the buoyancy force or (upthrust), is an upward force exerted by a fluid that opposes the weight of an immersed object. The center of buoyancy of an object is the centroid of the displaced volume of fluid.
The buoyancy force comes from the pressure exerted on the object by the fluid. Because the pressure increases as the depth increases, the pressure on the bottom of an object is always larger than the force on the top - hence the net upward force.
Formula:
Bf = W0 − WF
where,W0 = weight of object in empty space
WF = weight of object immersed in fluid
Bf = Buoyancy force