A method for storing a membership function, include storing a position of a vertex of a triangle that defines the membership function in a universe of discourse and storing a first distance between the position of the vertex a point of intersection between a left side of the triangle and an axis of the universe of discourse. Further, the method includes storing a second distance between the position of the vertex and point of intersection between right side of the triangle and the axis of the universe of discourse. The present invention furthermore relates to a circuit for calculating a grade of membership of an antecedent of a fuzzy rule, and is adapted to fuzzify an input variable by adopting the geometric proportions that occur between homologous sides of similar triangles defined by the position of the input value in the universe of discourse.