Electronics CalculatorsWhere to start
Begin with Ohm's law, then read about choosing an LED resistor, which is the first circuit most people build. The pages on E-series and power ratings help you choose parts you can really buy.
This is an independent guide. It is not connected with any standards body or company named here. The formulas are the usual textbook ones; the colour code, E-series and AWG values are those printed in common references, because the standards IEC 60062, IEC 60063 and ASTM B258 are paid documents that we did not read. Tables and examples were calculated with Python on 14 November 2026. Check data sheets and local safety rules before you build.