The living area calculation determines which parts of a dwelling are counted for rent or purchase price purposes. In Germany, the Residential Area Ordinance (WoFlV) of 2004 is the primary standard: full-height rooms count entirely, rooms with sloped ceilings partially, and balconies or terraces typically at one quarter. Basement rooms, staircases, and unheated spaces are excluded. Alternatively, DIN 277 may be contractually agreed upon, usually yielding larger figures. If stated living area deviates by more than ten percent from the actual measurement, tenants may be entitled to a rent reduction. Accurate figures are therefore legally and economically essential in both rental and purchase agreements.