Calculators and reference tools for electronics hobbyists
Reference tools and calculators for electronics work on the bench and at the desk. Resistor E-series lookup, series/parallel combinations, voltage dividers, LM317 regulator design, battery life estimation, LED current limiting — quick answers without opening a datasheet.
555 timer calculator for astable (oscillator) and monostable (one-shot) modes. Astable: R1, R2, C → frequency, period, duty cycle, tH, tL. Monostable: R, C → pulse width. Includes output waveform and pin reference.
Reference table for 78xx (positive) and 79xx (negative) fixed linear voltage regulators. Covers output voltages 3.3–24 V, current ratings, input range, dropout voltage, packages, and typical wiring diagrams.
Complete pin function reference for Arduino Uno, Nano, Mega, ESP32, and ESP8266. Filterable by PWM, ADC, I2C, SPI, UART, and interrupt functions. Includes boot-sensitive and input-only pin warnings.
Complete AWG wire gauge reference from 0000 to AWG 40. Diameter in mm and inches, cross-section in mm², resistance per metre and per foot, max current for chassis and power wiring. Includes EU metric equivalents and selection guide.
Estimate battery runtime from capacity and current draw. Supports multi-mode operation (active + sleep), efficiency factor, and includes a reference table for common battery types.
Calculate total voltage, capacity, and energy for batteries wired in series, parallel, or series-parallel (nSnP). Includes common LiPo/Li-Ion pack configurations and balancing tips.
Browse and search standard resistor values in E6, E12, E24, E48, E96 series. Enter any resistance and instantly find the nearest standard value with percentage error.
Select the right fuse for your circuit. Enter load current and application type (resistive, LED, motor, PSU) to get the recommended rating and type (fast/slow-blow). Includes IEC 60127 standard ratings table and housing reference.
LED forward voltage (Vf) reference by color and wavelength. Covers standard, high-brightness, IR, UV, white, and RGB LEDs. Includes semiconductor material, max current, Vf range bar, and resistor calculation guide.
Calculate the series resistor for an LED driven from a microcontroller GPIO pin. Platform presets for Arduino, ESP32, ESP8266, Raspberry Pi. LED colour selector, E12/E24 nearest values, GPIO current limit warnings, and circuit diagram.
Calculate the correct series resistor for an LED. Enter supply voltage, LED forward voltage and current — get resistor value, nearest E12/E24 standard value, and power dissipation.
Calculate R1 and R2 resistors for the LM317 adjustable voltage regulator. Shows nearest E12/E24 values, actual output voltage, power dissipation, and a circuit diagram.
Maximum GPIO current limits for Arduino, ESP32, ESP8266, Raspberry Pi, STM32, Teensy, and more. Per-pin absolute max, recommended safe current, and total package budget. Filterable and searchable.
Enter any 2 of 4 values (U, I, R, P) and get the remaining two. Visual Ohm's law triangle with highlighted known/calculated values.
Quick reference for 8 common op-amp configurations: comparator, voltage follower, inverting and non-inverting amplifiers, summing amplifier, differential amplifier, differentiator and integrator. SVG diagrams, formulas and gain calculator.
Calculate pull-up and pull-down resistors for buttons, open-drain outputs, and GPIO inputs. Shows idle state, current drain, RC time constant, rise time, and max toggle frequency. Includes application reference table and circuit diagram.
Calculate average output voltage from PWM duty cycle, or find the duty cycle needed for a target voltage. Shows tH, tL, period, analogWrite value, RC smoothing filter recommendation, and PWM waveform diagram.
Calculate RC low-pass and high-pass filter cutoff frequency fc = 1/(2πRC). Get attenuation at any frequency, attenuation table across decades, Bode plot, and circuit diagram.
Calculate RC circuit time constant τ = R × C. Three modes: R+C → τ, R+τ → C, C+τ → R. Charge and discharge tables with voltage at each multiple of τ, plus an interactive voltage vs time chart.
Decode resistor color bands to get resistance value, tolerance, and temperature coefficient. Supports 4, 5, and 6 band resistors. Includes reverse lookup — enter a value to find matching color bands.
Calculate power dissipated by a resistor. Enter any two of: voltage, current, resistance — get power, recommended wattage rating, and nearest standard resistor value.
Calculate total resistance for resistors in series or parallel. Add up to 8 resistors, see individual voltage/current distribution, nearest E12/E24 equivalent, and circuit diagram.
Calculate output voltage of a resistor voltage divider. Enter Uin, R1, R2 and optional load resistance — get Uout, current, power dissipation and load effect.
Calculate voltage divider resistors for safe ADC input. Platform presets for Arduino, ESP32, ESP8266, Raspberry Pi Pico. Auto-calculates R1/R2, shows ADC count, resolution, divider current, and utilisation. Includes warnings for over-voltage conditions.
Wire color code reference for AC mains, DC power, automotive, and data wiring. Covers IEC 60446, ČSN (Czech), old DIN, and US NEC standards with color swatches and searchable table.
Calculate the series resistor for a zener diode voltage regulator. Shows exact and nearest E12/E24 resistor value, zener current at full load and no load, power dissipation in R and zener, efficiency, and circuit diagram. Includes common zener diode reference table.