Knowing the engine size (V_eng) in liters, the vehicle mass (m_v) can be estimated with equation (1):

Where C_m depends on the vehicle type, as in the following table:

The mass factor (λ_m) is the relationship between the total mass of the vehicle (m_v) and the effective mass (m_e) of the vehicle, if we take into account the effect of the inertia of the rotating parts on the vehicle acceleration characteristics, such that:

Where F_net is the net thrust acting on the vehicle and a is its acceleration.

From Theory of ground vehicles (2^nd ed., p. 211), for passenger cars, an empirical relationship can relate the mass factor with the overall gear ratio (G):