The method for calculating airborne sound insulation between apartments as specified in DIN EN 12354-1:2000 has been used for many years -and is increasingly being used -in architectural design. This article will give a short overview of the basic principles of this calculation method, highlighting some special aspects, and will then focus on its application in practice. In particular, the experience gained with the KS Schallschutzrechner software (calculator for the prediction of sound insulation between dwellings and terraced houses ), which has now been in use for twelve years, demonstrates that -in spite of the improved prognostic accuracy -the method is not more labour-intensive than that of the previous procedure specified in DIN 4109 Supplement 1, provided suitable design aids are used.