Abstract: For nuclear-powered ships, the fast estimation of external gamma radiation dose is important for accident consequence evaluation and emergency response plan. However, currently there is no standard for the fast estimation of external gamma radiation dose in compartments. In this study, the results by MCNP calculations are used as a baseline to evaluate the accuracy of two methodologies, namely the finite cloud immersion method and the point-kernel integral method. Comparisons are performed for compartments with different shapes and volumes. The results show that the errors become larger if the shape of a compartment is more different from a hemisphere, or the volume of a compartment is larger; the error of the finite cloud immersion method is about 30%, while the error of the point-kernel integral method is about 10%. Therefore, the point-kernel integral method can provide more accurate and fast estimation for practical applications.