Abstract: There is a large error in calculating foundation settlement of small size by using the layerwise summation method based on consolidation tests, while the calculation of foundation settlement based on the plate load tests can not reflect the deformation characteristics of the foundations of large size. Considering the theoretical and experimental basis in calculating the foundations settlement under large-area loads by means of the layerwise summation method based on the e-pcompression curve, which can be deemed as the upper limit of the practical foundation settlement with the same base pressure, while p-ssettlement curve can reflect the deformation characteristics of the foundations of small size, which can be deemed as the lower limit of the practical foundation settlement with the same base pressure. Based on the above theory, an interpolation algorithm for the foundation settlement is proposed, and the issues of determining the modulus of compressibility are transformed into those of finding the interpolation functions. This algorithm can reduce the absolute error produced by the traditional algorithm to the relative error within a certain range so as to improve the calculation accuracy of foundation settlement. Furthermore, a method to predict the foundation settlement is suggested by adopting two load test results under different load plate sizes, whose rationality is verified through four-group plate load tests on the same foundation. And the interpolation function of a circle foundation is derived and analyzed to show the process of foundation settlement calculation through the interpolation method. The analysis results show that the foundation settlement curves gradually change from concave to convex when increasing the size of foundations. The proposed method combines the results of the consolidation tests and plate load tests, which can reflect the settlement characteristics of the foundations of different sizes. It is suitable for promotion in engineering practices with its clear theoretical and experimental basis and simple and convenient calculation process.