1. A method for estimating at least one control parameter of an injection system in an internal combustion engine for a target injection quantity, the method comprising the following steps: a) Determining at least one injection control grid with a plurality of grid points described by at least one grid parameter and one grid injection quantity in each case, while the injection control grid describes an operating range of the injection system, b) Determining at least one or a plurality of test points based on at least one or a plurality of isolated test injections of the injection system, while the test points are described by at least one test parameter and one test injection quantity in each case, and c) Estimating the control parameter of a target injection quantity with the aid of restricted linear regression between grid points and test points within at least one partial area of the operating range of the injection system.