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Electronics calculators
Calculations you need for building and repair, from Ohm's law and LED resistor sizing to DC-DC converters, the 555 timer, and solar panels. Each tool shows a circuit diagram or graph, and values update as you type.
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Basics
KB-09Ohm’s law calculatorEnter any two values: voltage, current, resistance, or power. The rest will be calculated automatically.KB-10Current power calculatorActive, apparent, and reactive power for DC, single-phase, and three-phase circuits.KB-11Resistor connection calculatorTotal resistance of any resistor combination and power dissipated by each resistor.KB-12Capacitor Combination CalculatorTotal capacitance for parallel and series connections, voltage across each capacitor, and stored energy.KB-13Electricity Consumption and Cost CalculatorHow many kilowatt-hours and how much money an appliance uses per day, month, and year.
Power supplies and converters
KB-14Buck converter calculatorInductor, output capacitor, duty cycle, and peak current for a DC-DC buck converter.KB-15Boost converter calculatorInductor, capacitor, duty cycle, and input current for a DC-DC boost converter.KB-16Linear Regulator CalculatorHow much heat a 7805 or LDO dissipates, its efficiency, and whether it needs a heatsink.KB-17LM317 CalculatorResistor values for the desired voltage, or an LM317 current regulator using E24 series values.KB-18TL431 CalculatorVoltage divider for the desired voltage and a ballast resistor for the adjustable shunt regulator.KB-19Rectifier Filter Capacitor CalculatorRequired capacitance after the diode bridge, output voltage, and allowable ripple.KB-20Power Transformer CalculatorPrimary and secondary winding turns, turns per volt, and wire diameter based on the core cross-sectional area.KB-21Power Supply Efficiency CalculatorHow much power a power supply draws from the mains, how much is lost as heat, and what it costs per year.KB-22LED Strip Power Supply CalculatorPower supply wattage, current, and number of connection points for a strip of the required length.KB-53Capacitive dropper calculatorBallast capacitor capacitance for a transformerless power supply, actual current, and protection resistors.
Batteries and solar power
KB-01UPS and inverter runtime calculatorHow long will a load run from a battery? Calculates for AGM, GEL, LiFePO4 and Li-ion batteries, accounting for inverter efficiency.KB-02Battery Pack CalculatorPack voltage, capacity, and energy, plus a layout of cells with different capacities across groups.KB-23Battery charging time calculatorHow long it takes to charge a battery, accounting for efficiency and the slow final stage.KB-24Battery C-rate calculatorConvert C-rate to amps and discharge time, and calculate heating from internal resistance.KB-25Power bank actual capacity calculatorHow many times a power bank will charge your phone, and its actual capacity at the 5 V output.KB-26Battery internal resistance calculatorBattery resistance from two voltmeter readings: with and without a load.KB-27Capacitor and supercapacitor energy calculatorHow much energy a capacitor stores and how long it can power a load.KB-28Solar power system calculatorPanel power, battery capacity, and controller current based on your daily consumption.KB-29Battery charge level calculator by voltageHow much charge is left in a Li-ion, LiFePO4, or lead-acid battery based on its resting voltage.
Components and circuits
KB-03LED resistor calculatorE12/E24 standard value, actual current and resistor power for a single LED or a string.KB-04Voltage Divider CalculatorFind the best feedback resistor pairs from the required series for DC-DC converters, with the error for each pair.KB-05Resistor codes: color bands and SMD codesDecode color bands (4, 5, and 6 bands) and SMD codes (3- and 4-digit, EIA-96), and find the code for a given value.KB-06LC Filter CalculatorCutoff frequency, characteristic impedance, Q factor, and DC-DC converter ripple attenuation.KB-30RC circuit calculatorTime constant, capacitor voltage at any moment, and time to charge to the desired level.KB-31Reactance and resonance calculatorCapacitor and inductor reactance at a given frequency, and the resonant frequency of an LC circuit.KB-32Capacitor markings: code decoderWhat do 104, 472J, 4n7, or 2A104K mean? Capacitance, tolerance, and voltage.KB-33Transistor base resistor calculatorWhat resistor do you need to reliably switch on a bipolar transistor from a microcontroller?KB-34MOSFET power loss calculatorConduction and switching losses, driver current, and junction temperature.KB-35Heatsink calculatorFind the required thermal resistance for a heatsink and estimate its area.KB-36Shunt calculatorShunt resistance and power for current measurement, plus the length of wire needed to make your own shunt.KB-37NTC thermistor calculatorThermistor resistance at a given temperature, and vice versa, plus divider voltage.
Signals and microcontrollers
KB-38RC Filter CalculatorCutoff frequency, attenuation, and phase shift for low-pass and high-pass filters.KB-39RMS, Peak, and Peak-to-Peak Voltage CalculatorConvert between RMS, peak, average voltage, and peak-to-peak voltage for different waveforms.KB-40Decibel calculatorConvert voltage and power ratios to and from decibels, and dBm to watts and volts.KB-41Operational amplifier calculatorGain of inverting and non-inverting circuits, output voltage, and bandwidth.KB-42NE555 Calculator: OscillatorFrequency and pulse duty cycle for a 555 timer in astable mode.KB-43NE555 calculator: timer, monostableSingle-pulse duration for a 555 timer and resistor selection for the desired timing.KB-44ADC calculatorLeast significant bit value, code for a given voltage, and conversion accounting for a voltage divider.KB-45Microcontroller timer PWM calculatorPWM frequency and resolution based on Arduino or STM32 timer settings, with TOP value selection.
Wires, boards, and coils
KB-07PCB trace width calculatorMinimum trace width based on current and temperature rise (IPC-2221), resistance, voltage drop, and losses.KB-08Wire Gauge CalculatorWire gauge based on current and voltage drop: copper and aluminum, low-voltage circuits, losses, and AWG.KB-46Wire voltage drop calculatorHow many volts are lost in a cable and what voltage remains at the load.KB-47Wire Resistance CalculatorResistance of copper, aluminum, steel, nichrome, manganin, and constantan wire, accounting for temperature.KB-48Nichrome Coil CalculatorThe length of nichrome or Kanthal wire needed for a heater of a given power, and its surface load.KB-49Inductor CalculatorInductance of a single-layer air-core coil, or the number of turns for a desired value.KB-50Toroidal Core Turns CalculatorHow many turns to wind for the desired inductance based on AL, and will the core saturate?KB-51Skin Effect CalculatorCurrent penetration depth and the maximum conductor diameter for a given frequency.KB-52AWG to mm² and diameter conversionOnline AWG table: diameter, cross-section, resistance per meter, and approximate current rating.
Frequently asked questions
Do I need to register to use the calculators?
No. All calculators are free and work without registration. Calculations run right in your browser; the values you enter aren’t sent anywhere.
What electronics calculations are available here?
Basics (Ohm’s law, power, resistor and capacitor combinations), power supplies and DC-DC converters, batteries and solar panels, components (MOSFETs, heatsinks, shunts, NTCs, markings), signals and microcontrollers (RC filters, NE555, ADC, PWM), wires and inductors.
Can I send my calculation to someone else?
Yes. The buttons below the calculator save your entered values in a link: the recipient will open the page with the same numbers and result.
