Electronics Calculators

Resistor Color Code

Decode 5-band resistor color codes to find the resistance value.

1st Digit

2nd Digit

3rd Digit

Multiplier

Tolerance

Resistance: 10 kΩ ± 1%

LED Resistor

Calculate the resistor needed for your LED circuit.

Supply Voltage (V)

LED Forward Voltage (V)

LED Current (mA)

Required Resistor: 150 Ω

Power Dissipation: 60 mW

Voltage Divider

Calculate output voltage from a resistor voltage divider.

Vin

R1

Vout

R2

GND

Input Voltage (V)

R1 (Ω)

R2 (Ω)

Output Voltage: 6.00 V

Ohm's Law

Enter voltage and current to calculate resistance and power.

Voltage (V)

Current (mA)

Resistance: 250 Ω

Power: 100 mW

Capacitor Code

Decode 3-digit ceramic capacitor markings to find capacitance value.

3-Digit Code (e.g., 104)

Capacitance: 100 nF

Also written as: 0.1 µF

555 Timer (Astable)

Calculate frequency and duty cycle for 555 astable oscillator.

R1 (kΩ)

R2 (kΩ)

C (µF)

Frequency: 4.81 Hz

Duty Cycle: 66.7%

RC Time Constant

Calculate RC time constant τ and charging/discharging times.

Resistance (kΩ)

Capacitance (µF)

Time Constant (τ): 1.00 s

63% Charge (1τ): 1.00 s

99% Charge (5τ): 5.00 s

Battery Life

Calculate how long your battery will last for a given load.

Battery Capacity (mAh)

Load Current (mA)

Battery Life: 20.0 hours

Also: 0.83 days

Inductor Reactance

Calculate inductive reactance (XL) from frequency and inductance.

Frequency (Hz)

Inductance (mH)

Reactance (XL): 62.83 Ω

Capacitor Reactance

Calculate capacitive reactance (XC) from frequency and capacitance.

Frequency (Hz)

Capacitance (µF)

Reactance (XC): 15.92 Ω

Frequency ↔ Wavelength

Convert between frequency and wavelength for RF and radio applications.

Frequency (MHz)

Wavelength (m)

Quarter-wave Antenna: 17.3 cm

Servo PWM

Calculate PWM pulse width for servo motor positioning.

Desired Angle (°)

Min Pulse (µs)

Max Pulse (µs)

Pulse Width: 1472 µs

Arduino Code: servo.write(90)