It is known that Fe Si super grains with typical grain size of 10-15nm are the basis of excellent soft magnetic properties. Understanding the microstructure of materials does not automatically lead to feasible and accurate material loss calculations. The limited material loss data provided by nanocrystalline core manufacturers, especially for frequencies above 100kHz, hinders the application of nanocrystalline materials to high-frequency magnetism. In this paper, the core loss density of nanocrystalline materials is measured for frequencies up to 500KHz and fluid densities higher than 1 Tesla. The analysis and calculation will also help to establish the core loss model for magnetic design. Ft-3m was selected as a mid range typical feature and availability.