Bremsstrahlung X-ray source term at 450 MeV was experimentally determined at booster synchrotron of Indus-l facility at Raja Ramanna Centre for Advanced Technology. Electron beam at 450 MeV extracted from booster synchrotron was allowed to fall on 25 rom lead target for the generation of the bremsstrahlung X-rays. The dose rate due to the X-rays in the forward direction was measured in 30 cm x 30 cm x 30 em water phantom using caSo₄:Dy thermoluminescent discs. The water phantom was placed at 1m from the target. Maximum dose rate obtained was 3.04 Gy/h at a depth of 5 em in the phantom. The experiment was simulated using EGSnrc code and the value obtained is 3.10 Gy/h at 5 em depth. The data is compared with the source term usually evaluated using the empirical relation suggested by W P Swanson, which gave 3.90 Gy/h. The experimental value is found to be in excellent agreement with the simulated dose rate. It is also found to be in good agreement with the value obtained from Swanson's empirical relation within ±28%.