Tools
Free electronics calculators
Small calculators for the values that come up every session: resistor codes, Ohm's law, LED resistors, voltage dividers and RC time constants. Free to use, no sign-up, and each one explains the formula behind the answer.
Free tool · Electronics
Resistor Colour Code Calculator
Pick the bands on a 4-band or 5-band resistor to read off its resistance and tolerance.
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Ohm's Law Calculator
Enter any two of voltage, current and resistance to find the third instantly.
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LED Resistor Calculator
Find the series resistor an LED needs from the supply voltage, forward voltage and current.
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Voltage Divider Calculator
Enter an input voltage and two resistor values to find the divided output voltage.
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RC Time Constant Calculator
Enter resistance and capacitance to find how fast an RC circuit charges and discharges.
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