Ohm's law calculator
Enter any two of voltage, current and resistance to get the other two, plus the power dissipated and whether a quarter-watt resistor will survive it.
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Fill in any two. Clear a box to solve for it.
Voltage
5 V
Current
22.7 mA
Resistance
220 Ω
Power dissipated
114 mW
Size the resistor at about twice this.
Where this comes from
The number is the easy part. If you have to explain it to a panel, read the write-up — it goes through the formula, the assumptions and the mistakes that make the answer wrong.
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