The foramen magnum is a large opening in the posterior part of norma basalis of human skull. Various vital structures pass through the foramen magnum including medulla oblongata and tonsil of cerebellum. So the measurements of the foramen are important as these structures may get compressed in disorders like foramen magnum herniation and achondroplasia. Fifty human skulls of unknown age and sex were included in the present study. The antero–posterior and transverse diameters were found to be 3.4 ± 0.3 cm and 2.79 ± 0.21 cm respectively as measured by digital slide calipers. The area of foramen magnum was calculated to be 7.49 ± 1.11 cm2  by suitable mathematical formula. These findings will be helpful for neurosurgeons, radiologists, anthropologists and forensic scientists.