Modelur is a simple, yet powerful parametric urban design software. Its performance-based nature enables it's users to quickly create massing studies of the proposed development based on key urban design parameters, such as Gross Floor Area or Number of Building Floors. It not only enables 3D modeling through parameters, but it also incorporates a real-time calculation of Urban Control Indicators, such as Floor Space Index or Required Number of Parking Lots. Additionally it also warns the user if the buildings are placed too close together. The main goal of Modelur project is to provide the tool to Urban Designer which is easy and intuitive to use. It is by no means a complete Urban Design package, nor it wants to be, but rather a quick sketching tool which helps it users make right and well informed decisions in the early phases of designing the city. Modelur is based on widely adopted 3D modeling application Trimble SketchUp and available for both Mac OS X and Windows operating systems. At the moment, it is available free of charge to anyone registered to Modelur Pre-beta Partner Program or through SketchUp's Extension Warehouse.