CircuitCalc
Ohm's law, LED resistor sizing, voltage dividers, resistor color codes, and RC time constants. No signup. Works on your phone at the bench.
Ohm's Law Calculator
Calculate voltage, current, resistance, or power. Enter any two values to find the rest.
LED Resistor Calculator
Find the right resistor for your LED. Enter supply voltage, LED forward voltage, and current.
Voltage Divider Calculator
Calculate output voltage or find resistor values for a voltage divider circuit.
Resistor Color Code Calculator
Decode 4-band or 5-band resistor color codes to find the resistance value.
RC Time Constant Calculator
Calculate the time constant, charge time, and cutoff frequency for an RC circuit.
About CircuitCalc
CircuitCalc is a collection of free electronics calculators for hobbyists, students, and engineers. Every tool runs entirely in your browser — no data leaves your device.
Whether you're sizing an LED resistor for a project, checking Ohm's law, designing a voltage divider, decoding resistor bands, or calculating RC time constants, these tools give you instant answers.
All calculations can be shared via URL — copy the address bar after calculating to share your exact inputs and results.