Calculators
All tools, organized by type. More added regularly.
Fundamentals
Core laws and relationships
Ohm's Law
liveSolve for voltage, current, resistance, or power. Enter any two values.
LED Resistor
liveFind the right current-limiting resistor for your LED. Don't fry it.
Color Code
liveDecode bands to value or find the bands for any resistance. 4- and 5-band supported.
Voltage Divider
liveCalculate output voltage, or find R1/R2 values for a target output.
Series / Parallel
liveCombine resistors or capacitors in series or parallel. Add as many as you need.
Analog
Passive component circuits
555 Timer
soonAstable and monostable modes. Frequency, period, duty cycle.
RC / Filter
soonTime constant τ, cutoff frequency, and charge/discharge curves.
Cap Charge
soonVoltage vs time during RC charge or discharge.
Battery Life
soonEstimate runtime from capacity and load current. Includes Peukert correction.
Wire Gauge
liveAWG to resistance and current capacity. Pick the right wire.
Active
Transistors, op-amps, regulators
BJT Bias
soonQ-point, base/collector/emitter voltages for common-emitter stage.
Op-Amp Gain
soonInverting and non-inverting configurations. Gain and resistor values.
LDO / 78xx
soonLM78xx series dropout, heat dissipation, and capacitor selection.
Zener
soonSeries resistor sizing for zener shunt regulator circuits.
Power & Signal
Power supplies, decibels, PWM
dB Converter
soonConvert between dB, voltage ratio, and power ratio.
PWM Voltage
soonAverage output voltage from duty cycle and supply.
Filter Cap
soonMinimum filter capacitor for target ripple voltage.
Transformer
soonTurns ratio, secondary voltage, and VA rating.
Digital / MCU
Microcontrollers and logic
I²C Pull-Up
soonOptimal pull-up resistor for I²C bus speed and capacitance.
GPIO Budget
soonTotal current draw across GPIO pins for Arduino / RPi.
Debounce RC
soonR and C values to debounce a mechanical switch input.
RF & Advanced
Frequency, resonance, transmission lines
LC Resonance
soonResonant frequency of an LC tank circuit.
Antenna
soonDipole and quarter-wave antenna length for a given frequency.
Reference
Codes, conversions, pinouts
SMD Code
soonDecode 3-digit and 4-digit SMD resistor markings.
Cap Code
soonDecode 3-digit ceramic capacitor codes to picofarads.
Unit Converter
soonConvert between mA/A, mV/V, pF/nF/µF, and more.