Electronics & Circuits Calculators
The everyday bench tools for building circuits — decode a resistor's color bands or a capacitor's code, size an LED resistor, work out a voltage divider or RC filter, design a 555 timer, look up a wire gauge, and estimate battery life. Standard formulas and reference tables, running entirely in your browser.
- Resistor Color Code Calculator Pick the color of each band to read a resistor's value and tolerance
- LED Resistor Calculator Enter your supply voltage, the LED's forward voltage and its current to get the exact series resistor
- Voltage Divider Calculator Enter the input voltage and the two resistors to get the divider's output voltage, the current it draws and the power it dissipates.
- Capacitor Code Calculator Enter a ceramic capacitor's printed code
- Wire Gauge (AWG) Calculator Choose an AWG size to see its diameter, cross-section, copper resistance per length and typical current rating.
- RC Time Constant & Filter Calculator Enter a resistance and capacitance to get the RC time constant and the filter's cutoff frequency.
- 555 Timer Calculator Enter your resistors and capacitor to get the 555's output frequency and duty cycle
- Battery Life Calculator Enter your battery capacity and the device's current draw to estimate how long it will run.
- SMD Resistor Code Calculator Type the number printed on a surface-mount resistor to read its resistance
- LC Resonant Frequency Calculator Enter an inductance and capacitance to get the LC circuit's resonant frequency and its characteristic impedance.
- Ohm's Law Calculator Enter any two of voltage, current, resistance and power, and the calculator fills in the other two using Ohm's law.
- Series & Parallel Resistor Calculator Enter a list of resistor values and get the total resistance both in series
- Series & Parallel Capacitor Calculator Enter a list of capacitor values in µF and get the total capacitance both in parallel
- Reactance Calculator (Xc & Xʟ) Enter a frequency and a capacitance or inductance to get its reactance
- Decibel (dB) Calculator Convert a ratio to decibels or decibels to a ratio, for power
From color bands to working circuits
Two things dominate the electronics bench: reading component markings and applying a handful of formulas. The resistor color code and 3-digit capacitor code pack a value into a few bands or digits, and these tools decode them instantly (with a live picture of the resistor). The rest is Ohm's law and a few standard relations — the series resistor an LED needs, how two resistors divide a voltage, the time constant and cutoff of an RC pair, and the frequency of a 555 timer — each shown with the equation so the tool teaches as it calculates.
Everything runs in your browser, so it's fast, private and works offline at the bench. One safety note: the wire-gauge current ratings are conservative guidelines, and anything involving mains voltage or building wiring must follow your local electrical code. For the underlying theory — Ohm's law, energy and the resistor/capacitor networks — see the Physics category.
Frequently asked questions
Are these electronics calculators accurate?
Yes — they use the standard tables and textbook formulas: the IEC 60062 resistor and capacitor color codes, the AWG diameter equation and copper resistivity, the NE555 timer equations, and Ohm's law. The data was cross-checked against IEC, manufacturer datasheets and NEC references.
Do these replace a datasheet or electrical code?
No. They're design aids for hobby and learning use. For anything involving mains voltage, building wiring or safety-critical current ratings, always follow your local electrical code and the component datasheets, and consult a qualified professional.
Is my data uploaded?
No. Every tool runs entirely in your browser — nothing is sent to a server, and they work offline.