A load estimating system which estimates a load of a database, includes a storage unit, a record number calculating module, and an access number calculating module. The storage unit includes structure information defining a structure of a table in said database, first distribution information indicating probability distribution of condition variables of a query for said table, and second distribution information indicating probability distribution of values in said table. The record number calculating module calculates the average number of selected records which meet conditions defined by-condition variables, based on said structure information, said first distribution information and said second distribution information. The access number calculating module calculates the number of block accesses for said query based on the average number of selected records.