Abstract: A method of estimating the time a particular designer or any one of a group of designers will take to realize a new design using an object-oriented methodology. The particular version, for each designer, or group of designers, of a formula which links time taken and the number of predetermined types of object-oriented elements, each element type having a respective multiplier for each designer or group of designers, is determined by “training” using the number of the elements employed and the actual time taken, for a number of previous designs, realized by that designer or group of designers. For the new design, the numbers of the elements to be present is determined and this data inserted into the formula with the respective designer's designers' multipliers and an estimate of time obtained.