Abstract: To obtain the effort of software projects,an effort estimation method based on software size is presented. First,the linear relationship between software effort and size is determined by the scatter diagram generated by the organizations historical data. Next,the formula statistics method and the tool statistics method are adopted independently for linearity regression analysis. After the regression analysis, the linearity regression equation is obtained,according to which the effort could be got.To simplify the calculation process,the programming statistics method is also studied. The final study indicates that the outcomes obtained by these three methods are almost consistent. The application of the linearity regression equation proves that these three methods are effective and they could be applied in most software organizadons. The estimation error is not higher than 33.57%.

Key words: software size, effort estimation, formula statistics, tool statistics, programming statistics