current equation for hand calcultations in 65 nm technology...?

i have to work on UMC 65nm...BSIM3 model has more than 50 parameters in current equation. Is there any equation for hand calculation for saturated current in mos. Even if the output lies in range of 10-20% it's k for me..I mean idsat=kn[(Vgs-Vth)^2]/2 will it work normally in 65nm?

Current equations are found in any texbook but the best way to check the accuracy of this equation is to simulate with-for instance- Cadence or HSPICE.
Because foundry MOS models are generally are very complex so that it doens't permit to calculate the current density in the channel by hand.
The equations which are given in those textbooks is to give an idea about MOS behaviour and characteristics but reality is pretty far.