Electronics Tools

Free electronics and electrical-engineering calculators that run entirely in your browser — Ohm's law, resistor and capacitor codes, series/parallel resistance and capacitance, 555 timer, RC/RL time constants, LC resonance, reactance, filter cutoffs, AWG wire gauge, voltage drop, dBm, decibels, transformer ratios and battery life. No sign-up, nothing uploaded.

Resistor Color Code

Decode a 4-band resistor color code into its resistance value and tolerance.

ΩV

Ohm's Law Calculator

Solve for voltage, current, resistance and power from any two known values.

LED

LED Resistor Calculator

Find the current-limiting resistor for an LED, plus the nearest E12 value and power.

V÷

Voltage Divider Calculator

Compute the output voltage and current of a two-resistor voltage divider.

Electrical Power Calculator

Compute power, voltage, current or resistance from any two known values.

λf

Wavelength & Frequency

Convert between wavelength and frequency for light, sound or a custom wave speed.

🔌

Capacitor Code Calculator

Decode a 3-digit capacitor code to pF, nF and µF with tolerance, or convert a value back to its code.

🔗

Series & Parallel Resistor Calculator

Add resistors in series or parallel, and reverse-solve the second resistor for a target combined value.

⚡

Series & Parallel Capacitor Calculator

Combine capacitors in series or parallel into one equivalent value, auto-scaled to pF, nF or µF.

⏱️

555 Timer Calculator

Compute 555 astable frequency, period, duty cycle and high/low times, or the monostable pulse width.

🔋

RC / RL Time Constant Calculator

Find the RC or RL time constant, the 1τ–5τ charge levels, and voltage at any time while charging or discharging.

📻

LC Resonant Frequency Calculator

Solve LC resonance for frequency, inductance or capacitance, plus the reactance at resonance.

〰️

AWG Wire Gauge Calculator

Convert an AWG number to wire diameter, cross-section area, resistance per length and rough ampacity.

📉

Voltage Drop Calculator

Estimate wire voltage drop, percentage and voltage at the load from current, length, AWG and material.

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Battery Life Calculator

Estimate how long a battery lasts from its capacity and load, with a realistic derating factor. Works in mAh/mA or Wh/W.

📶

dBm / Watts / Volts Converter

Convert RF power between dBm, watts, milliwatts and volts RMS for any impedance. Enter one value, get the full set.

🌀

Inductive & Capacitive Reactance Calculator

Compute inductive (XL) or capacitive (XC) reactance, or solve for frequency, inductance or capacitance, with unit selectors.

🎚️

RC / RL Filter Cutoff Calculator

Find the −3 dB cutoff frequency of an RC or RL low-pass or high-pass filter, or solve for the resistor, capacitor or inductor.

🔁

Transformer Turns Ratio Calculator

Find a transformer's turns ratio from primary and secondary voltage, plus secondary turns and current and step-up/down type.

📊

Decibel Gain / Ratio Calculator

Convert between a decibel gain and a linear ratio for power or voltage, or find the dB gain between two values.

⚡

Battery Capacity Converter (mAh ⇄ Wh)

Convert battery capacity between mAh and Wh using the nominal voltage, and see the equivalent in kWh.

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