Electronic Components
LED Resistor Calculator
Use LED Resistor when series resistance is the quantity you need. Enter supply minus LED voltage and LED current, then compare the answer with the equipment or operating limits that apply to your case.
Run the LED Resistor scenario
Keep every entry on the units shown below.
Input notes
Keep nominal component markings separate from measured operating values. If operating conditions changed between readings, calculate separate cases.
At least one field has a positive lower bound because it appears in a denominator. Use the displayed unit for every field and document conversions separately. For the companion total LEDs calculation, open LED Array Configuration Calculator.
- Supply minus LED voltage
- Default example: 7 V. Enter supply minus LED voltage in V.
- LED current
- Default example: 0.02 A. Enter LED current in A.
Understanding the equation
Here, Series resistance is obtained from R = voltage drop ÷ LED current. Only Supply minus LED voltage and LED current enter the numerical result.
Using the loaded examples gives 350.00 Ω. Your saved case should identify where each entry came from.
Calculate series resistance from supply minus LED voltage and LED current. A later series resistor decision can draw on Zener Resistor Calculator.
Interpreting the answer
Use Series resistance as one quantified check within the larger decision. Compare it with minimum, nominal, and worst-case component values.
Keep the input set beside the output so another reader can reproduce it.
Transferring the result
Archive supply minus LED voltage and LED current with series resistance. Identify the instrument, rating, or assumption behind each entry.
Transfer series resistance with all available digits during downstream arithmetic. Keep a separate displayed value if reporting precision differs.
Where this estimate can fail
Choose a resistor power rating with margin.
The arithmetic intentionally leaves out pulse ratings, frequency behavior, package temperature, and layout. Test an additional scenario when an omitted effect has a plausible range.
Keep nominal component markings separate from measured operating values.
A final reasonableness check
Begin by confirming LED current at the operating point represented by the other entries. Record whether it came from a meter, nameplate, data sheet, or design assumption.
The displayed series resistance should be checked against the selected component data-sheet limits. Investigate an unexpected magnitude before changing the model or adding margin.
Document any effect handled outside this page, especially bias dependence, ESR, leakage, saturation, and self-heating. That note prevents a later reader from assuming the simple equation covered it.
Questions about LED Resistor
Why does the field result disagree with this page?
Differences can come from parasitics, layout inductance, tolerance stack-up, switching edges, and thermal resistance, measurement uncertainty, or values taken under different conditions.