You need a certain inductance and looking for the corresponding number of turns, but don’t have the equations on hand or do not have all the data on the cores you have. What do you do? The answer is to use Mini Ring Core Calculator software. It can do calculations for all kinds of inductors (Iron Powder Cores (AMIDON), Unknown Cores, Air Cores, Ferrite Cores (AMIDON), Ring Cores from EPCOS, Ring Cores from Ferroxcube (Philips)). In addition there are tools to help determining permeability of unknown cores. Who needs such a calculator? – Radio amateurs and other electronics hobbyists, who are still home brewing. The software is free and runs on Windows. When working with homebrew inductors, keep this program and RLC meter nearby.
Mini dB calculator is a dB-Calculation for the experimenting radio amateur. Pick that software as well. It can do all kind of dB calculators stating from voltage to dB conversions to cable loss and EIRP/ERP calculations.