Free tools

Calculators for the first sketch.

Quick estimates to reason about a circuit. They are simplified teaching tools, not a substitute for measurement, a datasheet, or a safety review.

Calculator

Explore the relationship between voltage, current, and resistance with a simplified calculation.

Calculator

Estimate a series resistor for one LED using your supply voltage and LED assumptions.

Calculator

Estimate power dissipation in a resistor from electrical values.

Calculator

Combine 2–20 resistor values into one equivalent resistance, with clear series and parallel assumptions.