In Physics, force is any movement that occurs on an object when an external object is acted upon it. It is the push or pull that can cause an object with mass to accelerate. The acceleration of the object is directly proportional to the force and inversely proportional to the mass of the object. Here is a simple force calculator, to calculate the force which is expressed in Newton. Alternatively, you can also calculate mass, acceleration with the other known values.
A body with mass 20 kilograms and acceleration 5 m/s2 will have a force
Mass = 20 kgs
Acceleration =5 m/s2
= 20 x 5
= 100 Newtons