warm up time is significant for a Siemens Linac. Machine input parameters such as gantry speed, MLC speed and delay and RF wave time were confirmed using a WIN (Sports timer) stop watch. We tested our derived model by selecting ten random prostate IMRT plans from our clinic. These treatment plans were delivered on the Linac and measured. Results: The delivery time measured was between 314 s and 480 s. The largest percentage difference between measured and calculated was 3.9% (13 s) and the smallest was 0.2% (1 s). The average percentage difference was 1.78%. These results correlated well with published reports. These differences seem to be insignificant, 99% CI [408; 400]. Conclusion: Deriving a time delivery model makes it possible to estimate the time delivery before dose delivery is done on a Linac. This is important since we can choose a plan, from a pool of clinically acceptable plans, with the shortest delivery time, and thus increase dose delivery accuracy by minimizing patient movement.