The working of the beam balance is based on the principle of moments. The principle of moments states that the sum of the clockwise moments on a beam must be equal to the sum of the counterclockwise moments on the beam. This means that the weight of the object on the left side of the beam must be multiplied by the distance from the fulcrum to the left side of the beam, and the weight of the object on the right side of the beam must be multiplied by the distance from the fulcrum to the right side of the beam. If these two products are equal, then the beam will be in equilibrium.