Free electronics calculators — 15+ tools

Electronics calculators do the arithmetic that sits between a circuit on paper and a circuit that works. Pick the wrong resistor and an LED burns out; misjudge a wire run and the voltage sags before it reaches the load. These tools size those parts for you from the same equations an engineer uses, so you get a number you can build with instead of a guess.

Ohm’s law is the foundation — voltage, current, resistance, and power from any two values. From there the practical tools branch out: an LED series resistor and a series/parallel resistor solver, a resistor color-code decoder, a voltage divider, and a voltage drop tool for wire runs. For AC and timing there is a capacitor and an LC resonant-frequency calculator, a precision Wheatstone bridge, and an electricity cost estimator for what a device adds to the bill.

Every formula is the textbook standard — Ohm’s law (V = IR), the power law (P = VI), the resistor-network and divider equations, and the LC resonance formula f = 1 / (2π√(LC)) — and each page shows the equation, the units, and a worked example. The results are exact for the values you enter; real parts carry tolerances (a ±5% resistor, an electrolytic capacitor that drifts with age and temperature), so treat the output as the design target and check against the parts you actually use.