LED Resistor Calculator
Compute the series resistor for an LED: R = (V_cc − V_f)/I.
Input Data
Supply Voltage V
V
Led Forward Voltage V
V
Led Current Ma
mA
Results
R = (V_cc − V_f)/I.
150Ω
P = I²R.
0.06W
Nearest standard E24 value.
150Ω
At a glance:R = (V_cc − V_f)/I; choose the next higher E24 value. Complements led and ohm's-law.
Formula
R = (V_cc − V_f) / I.
$$R = \frac{V_s - V_f}{I}, \quad P_R = I^2 R$$How to Use
- Enter supply, V_f and current.
- The tool returns R and power.
Case Studies
V_cc=5, V_f=2, I=20 mA
R = 150 Ω.
FAQ
Pick higher R?
Yes — never below calculated to avoid overcurrent.
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References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.