Engineering calculators

Everyday calculations for hardware engineers: Ohm's law, dividers and feedback resistors, LED resistors, RC filters, colour and SMD codes, E-series values, PCB trace width, junction temperature, UART baud error and dBm. Everything runs in your browser.

Basic circuits

Ohm's law / powerEnter any two of voltage, current, resistance and power to get the rest.Voltage divider / feedback resistorsDivider output voltage, and the best E-series resistor pairs for DC-DC / LDO feedback.LED series resistorSeries resistor from supply, forward voltage and current, with the standard value and its dissipation.RC / LC filter & time constantRC cut-off frequency, time constant and charge times; LC resonance and characteristic impedance.

Component codes & values

Resistor colour codeRead 4/5/6-band resistors, or enter a value to get its bands.SMD resistor / capacitor codesDecode 103, 4R7, 1002, 01C (EIA-96) resistor markings and 104, 4N7 capacitor codes.E-series standard valuesRound a calculated value to the nearest E6/E12/E24/E96 standard value and show the error.

PCB & thermal

PCB trace width / currentIPC-2221 minimum trace width for a current and temperature rise, or the current a width can carry, plus resistance and drop.Junction temperatureEstimate junction temperature from power, ambient and θJA; the LDO mode derives power from the voltage drop.

MCU & RF

UART baud rate errorUSART divider register (BRR on STM32/GD32/AT32/CH32, UBRR on AVR) and the real baud rate error for a peripheral clock.dB / dBm converterConvert dBm, watts and RMS voltage (any impedance), and voltage / power ratios to dB.

Site tools

Marking code lookupFind a part by its top markingParametric searchFilter chips by parametersFull-text datasheet searchSearch inside datasheetsBOM toolPaste a BOM, match every datasheet