Free tools for makers, students, and engineers. Calculate resistor values, LED circuits, voltage dividers, and more — right in your browser.
Decode 4-band and 5-band resistor color codes instantly. Get resistance value, tolerance, and multiplier.
Calculate the correct current-limiting resistor for your LED circuit. Supports multiple LEDs in series.
Calculate output voltage, resistor values, or current for a resistive voltage divider circuit.
Calculate voltage, current, resistance, and power — enter any two known values to solve the rest.
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