This document compares the economical aspects of long span flat slabs and grid slabs. Flat slabs are modeled using the direct design method, while grid slabs are modeled using plate theory. The cost is calculated based on the quantity of steel, concrete volume, and formwork costs. For spans ranging from 5-13 meters, the cost per square meter is determined for different slab designs. The results show that flat slabs are more economical for smaller spans, but grid slabs become more economical for longer spans above 9 meters.