Since there is no reliable surface-area formula available for the calculation of the heat-transfer characteristics of an insulated oblate spheroid, in this investigation, highly accurate oblate spheroid surface area is obtained by a simple numerical integration method. Based on the accurate oblate spheroid surface area a, reliable one-dimensional approximate solution of an insulated oblate spheroid container can be obtained with a one-dimensional RPSWT model. By comparing with accurate three-dimensional numerical results, it is found that in cases of low external convective coefficient (h(o) = 8.3 W m(-2) K-1), long-short-axes ratio a/b <= 3, and insulation thickness t/R-2 <= 2, errors are within 3%. In rarer situations with a/b <= 5 and t/R-2 <= 2. the errors are within 5.5%. The above results are almost independent with the internal flow convective coefficient (h(i) from 30 to 10(5) W m(-2) K-1) and dimensionless container size (0.5R(2)h(o)/Ks from 1.55 to 155). (C) 2009 Elsevier Ltd. All rights reserved.