All tools
Every calculator, one page.
7 electronics calculators. All client-side, all free, no signup.
Resistor Color Code Decoder
Decode 4-band, 5-band, and 6-band resistors. Reverse lookup: type a value, get the color bands.
↳ 4.7 kΩ · ±5% · Brown Black Red Gold
Ohm's Law Calculator
Enter any two of V, I, R, P — get the other two instantly. Includes power triangle diagram.
↳ V = 12 V · I = 240 mA · R = 50 Ω
Voltage Divider Calculator
Live schematic, optional load resistance, power dissipation per resistor. Most tools skip the load — this one doesn't.
↳ Vin 5 V · R1 10 kΩ · R2 6.8 kΩ → Vout 2.07 V
Parallel & Series Resistor Calculator
Add up to 8 resistors in parallel or series. Shows equivalent resistance and nearest E24 standard value.
↳ 1 kΩ ∥ 1 kΩ ∥ 2.2 kΩ = 421 Ω → E24: 430 Ω
LED Resistor Calculator
Required resistor, nearest standard value, and power rating from supply voltage and LED specs. Color presets included.
↳ 5 V · Red LED (2 V, 20 mA) → 150 Ω, ¼ W
RC Time Constant Calculator
τ, charge/discharge times, and cutoff frequency from R and C. Animated charge curve updates on every keystroke.
↳ 10 kΩ · 100 nF → τ = 1 ms · fc = 159 Hz
555 Timer Calculator
Frequency, period, and duty cycle for astable oscillators; pulse width for monostable one-shots. Live schematic and waveform.
↳ R1 1 kΩ · R2 10 kΩ · C 100 nF → 660 Hz · 52% duty