How to calculate the power required during transition from VTOL to fixed wing?

In a VTOL, I have calculated the power required for take off and cruise which was not difficult at all. Between take off and cruise, there is a phase where the VTOL has to transition by tilting the rotors from 0 to 90 deg. I am finding it hard to calculate the power required for this transition. I feel this is very important because it consumes more power than take off since it is creating lift (hasn't reached the minimum velocity for the lift requirement) for balancing weight and also needs to provide thrust for forward motion. Given to me are:

1. Rotor parameters

     number of rotors
Rotor diameter
rpm

       span and chord (rectangular wing)