LED Resistor Calculator
Enter supply voltage, LED forward voltage, target current, and series LED count to estimate the ideal current-limiting resistor and a rounded-up common resistor candidate.
- Total LED forward voltage
- V
- Resistor voltage
- V
- Ideal resistor value
- ohm
- Resistor power
- W
- Rounded-up common resistor candidate
- ohm
Calculation details
- Calculation basis
- Component boundary
Recent results
Formulas
- Total LED forward voltage = LED forward voltage x series LED count
- Resistor voltage = supply voltage - total LED forward voltage
- Resistance = resistor voltage / LED current in amperes
- Resistor power = resistor voltage x LED current in amperes
- Common candidate = rounded-up E12-style resistance candidate
Use this calculator
Estimate the resistor value and resistor power for a simple series LED circuit.
Read the result
Review the calculated values with their displayed units and assumptions. The result is a planning aid for the stated inputs, not a final equipment or installation decision.
Check before final work
This LED resistor estimate uses entered forward voltage and current assumptions. It does not model current regulation, LED temperature, tolerance, pulse behavior, supply variation, thermal limits, or product safety.
FAQs
Does this choose the final LED resistor?
No. It estimates ideal resistance and a rounded-up common-value candidate. Verify LED data, resistor tolerance and wattage, temperature, supply variation, and the actual circuit before use.
Why does the calculator round the common value up?
A rounded-up resistance tends to limit current below the ideal target under the stated voltage and forward-voltage assumptions. It is still only a candidate for review.