QBlade is an open source wind turbine calculation software, distributed under the GPL. The integration of the XFOIL/XFLR5 functionality allows the user to rapidly design custom airfoils and compute their performance polars and directly integrate them into a wind turbine rotor design and simulation. The software is especially adequate for teaching, as it provides a ’hands on’ design and simulation capabilities for HAWT and VAWT rotor design and shows all the fundamental relationships of design concepts and turbine performance in an easy and intuitive way. QBlade also includes extensive post processing functionality for the rotor and turbine simulations and gives deep insight into all relevant blade and rotor variables. In addition to that, the resulting software is a very flexible and user-friendly platform for wind turbine blade design.