⌁BenchSupply

Free practical electronics tools

Get the numbers right before you power it.

Fast, plain-English calculators for breadboards, repairs, hobby projects and first prototypes. No login, no spreadsheet and no hidden units.

The essential one

Ohm’s law calculator

Enter any two values and leave the value you want calculated blank.

This is DC / simple resistive-load arithmetic. Components can heat up, supplies have limits and AC circuits need impedance rather than simple resistance.

More tools

From a quick LED to a complete timing circuit.

LED resistor calculator

Set LED current, series count and supply voltage, with a practical resistor recommendation.

Voltage divider

Calculate output voltage, current and resistor dissipation.

Battery runtime

Estimate usable watt-hours and runtime with a transparent efficiency allowance.

Resistor colour code

Turn four colour bands into resistance and tolerance.

555 astable timer

Frequency, period and duty cycle for the classic two-resistor circuit.

RC time constant

Time constant, cutoff frequency and a practical settle-time estimate.

Built for checking

Small calculations have expensive failure modes.

A decimal point, unit mismatch or warm resistor can turn a five-minute project into a damaged part. BenchSupply keeps the formulas visible in the surrounding explanation and uses practical defaults—not magic answers.

Use the result to choose a safe starting component, then check its data sheet, ratings and your full circuit.