Calculating sound insulation between rooms is an important part of engineering design, because it is necessary to keep specific noise limits. A program that can estimate acoustic performance of buildings from the performance of elements, can be helpful for a designer engineer. In the present thesis a software is introduced, which is able to do estimation on the basis of MSZ EN 12354-1:2000 Standard. During my work I get to know the Standard, the concept of sound reduction and the necessary quantities and methods for calculation. I examined two similar program for estimating sound reduction. I compared their usability and I designed my own software. I added a userfriendly graphical interface to my main program. In order to check wheather the operation of my finished program is correct I compared its results to other softwares’ results and I also tested the examples given in Standard MSZ EN 12354-1:2000. Accordig to the tests my program is basically correct, the cause of differences emerged are investigated.