Hi,
I think that it must be done via formula extracted from the parameters:

ω_T=gm/C_gs

Hope it helps,

Hi Vivek,
Usually I use only aproximations and then I do the fine tunning, if you want to do the correct calculation of ft I think you should go to the definition:frequency at which current gain it's zero, I did this simulation in the past using the parameter h21 but not in spectre(I used ATLAS for modelling a device) but if I remeber right sp analysis of spectreRF calculates hybrid parameters as well(I cannot check right now because our license server is down...), another possibility I suppose will be to calculate the Cgs using calculation taking into account gate channel and overlap capacitances but I then you should dig into geometrical parameters of transistor that I don't know if can be accesed directly using op of dc analysis.
Hope it helps,