I’m working on some SMPS hacks these days and i was looking for an online calculator for flyback transformers to avoid all the tedious and nasty job of complex calculations, when i came across this wonderful tool from NXP. The NXP Flyback SMPS Design Tool helps you design flyback power supplies using NXPs TEA1721, TEA1723, TEA1733 and TEA1738 family. The TEA1721(A, B, D, F) family, the TEA1723(A, B, D, F) family, the TEA1733(A, B, C, M, L) family and TEA1738(F, G, L) family are low cost Switched Mode Power Supply (SMPS) controller IC 19s intended for flyback topologies.
Its useful even if you do not want to use the TEA family chips! Check this out in this link