Electronics Calculators

18 free electronics calculators for Ohm's law, LED resistors, voltage dividers, battery life, 555 timers, and more. No signup required.

18 free tools

Ohm's Law Calculator

Enter any two of voltage, current, or resistance to solve for all four values including power.

LED Resistor Calculator

Find the correct current-limiting resistor for any LED with exact and nearest E24 standard value.

Resistor Color Code Calculator

Decode resistor color bands to ohm values or encode a resistance value to color bands. Supports 4-band and 5-band resistors.

Voltage Divider Calculator

Output voltage from two series resistors and an input voltage with current and division ratio.

Battery Life Calculator

Estimate battery runtime from mAh capacity and mA current draw in hours and days.

Power Consumption Calculator

Electricity cost and kWh for any device. Enter watts, hours per day, and rate for daily, monthly, and yearly cost.

Wire Gauge Calculator

AWG wire gauge specifications and minimum gauge recommendation for a given current load.

Capacitor Value Calculator

Decode ceramic capacitor 3-digit codes to pF, nF, and µF, or encode a value to its marking code.

UPS Sizing Calculator

Find the correct UPS VA rating for your equipment from total watts and power factor.

555 Timer Calculator

Calculate 555 timer frequency, period, and duty cycle for astable mode or pulse width for monostable mode.

Voltage Drop Calculator

Voltage drop in a wire run from source voltage, current, AWG gauge, and one-way distance.

Power Factor Calculator

Calculate power factor, reactive power in VAR, and phase angle from real power and apparent power.

Resonant Frequency Calculator

LC resonant frequency from inductance and capacitance values with unit selectors for H, mH, µH, F, mF, µF, nF, pF.

Wheatstone Bridge Calculator

Find the unknown resistance in a balanced Wheatstone bridge from three known resistors.

RMS Voltage Calculator

Convert between RMS voltage, peak voltage, peak-to-peak voltage, and average voltage for sine waves.

Transformer Calculator

Secondary voltage, turns ratio, and secondary current from primary voltage and either secondary voltage or turns ratio.

Capacitor Energy Calculator

Energy stored in a capacitor and charge on its plates from capacitance and voltage.

RC Time Constant Calculator

RC circuit time constant tau, full charge time at 5 tau, and percent charged at 1, 3, and 5 tau.