LED Resistor Calculator
Calculate resistor value and power rating to limit LED current.
Result
Complete the fields to calculate.
Formula and method
R = (Vs − Vf) / I
Important assumptions
Forward voltage varies by LED, current, and temperature. The E12 value is rounded up and the rating includes headroom.
Frequently asked questions
Does the calculation run locally?
Yes. Values are processed in your browser and are not sent to a server.
Can I use it for a real installation?
Use it as an educational reference and verify components, tolerances, safety, and applicable code with technical documentation or a qualified person.
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