Gravitational constant is equal in magnitude to that force of attraction which acts between two particles each of unit mass separated by a unit distance apart. ∴G=m1m2Fr2
(Newtons law of gravitation) where m1 and m2 are masses, r is the distance between them, and F is force. ∴ Dimensions of gravitational constant =(dimensionsofmass)2dimensionsofforce×(length)2 =[M2][MLT−2][L2] =[M−1L3T−2]