An egg‐shaped body is defined mathematically in terms of three parameters: L, its length along the axis of symmetry; b, the ratio of its maximum breadth to its length; and p, which is given by the equation where Xm is the distance from the narrow pole to the plane of maximum breadth. The volume, V, of such a body is given by the equation where V1 is the volume of a similar body of unit length and is given by Comparison of the volumes of hens’ eggs measured by water displacement with the volumes calculated from these equations showed a very high correlation (r = + 0.994). The surface area, S, of the ovoid of length L is given by the equation where S1 is the surface area of a similar ovoid of unit length. St is the sum of a rapidly converging infinite series the terms of which are functions of b and p. A table gives values of V1 and S1 for ovoids having values of b and of (L‐Xm)/L found in hens’ eggs.