Estonian oil shale reserves have been estimated proceeding from the requirements of power plants. Today, when the possibility of selling shale oil in larger amounts is becoming a reality, the oil shale reserve has to be evaluated according to the criteria of oil production. The solid-energy-carrier method of processing as a relatively new way of oil generation has economical advantages and has therefore to be considered at calculating cutoff grade for mining. The basis for using this approach has been worked out by GIS modelling. Preliminary calculations showed that the cut-off grade of oil shale could be lower than today's 35 GJ/m(2). This could increase the mineable resource of Estonian oil shale.