LED Resistor Calculator —
Basic
Basic
Pro
Battery
AA / AAA (1× = 1.5V)
Coin Cell CR2032 (≈3V)
2× AA/AAA (3V)
3× AA/AAA (4.5V)
4× AA/AAA (6V)
9V rectangular
8× AA/AAA (12V)
Arduino 5V (USB / 5V regulator)
Arduino 3.3V (3V3 rail)
Custom…
Custom Battery Voltage (V)
Number of LEDs (series)
LED Forward Voltage
Red (≈2.0 V)
Amber (≈2.1 V)
Green (≈2.2 V)
Blue (≈3.0 V)
White (≈3.2 V)
Custom…
Custom LED Vf (V)
LED Current (mA)
Calculate Resistor
Reset
Formula: R = (V
supply
− N·V
f
) / I. One resistor for a series string of LEDs.
Supply
AA / AAA (1× = 1.5V)
CR2032 coin cell (≈3V)
2× AA/AAA (3V)
3× AA/AAA (4.5V)
4× AA/AAA (6V)
9V rectangular
8× AA/AAA (12V)
Arduino 5V (USB/5V rail)
Arduino 3.3V (3V3 rail)
Custom…
Custom Voltage (V)
Supply Ripple / Headroom (%)
Topology
Mode
Single series string (1 resistor)
Parallel strings (1 resistor per string)
LEDs per string (series)
Number of parallel strings
LED Parameters
LED Forward Voltage
Red (~2.0 V)
Amber (~2.1 V)
Green (~2.2 V)
Blue (~3.0 V)
White (~3.2 V)
Custom…
Custom Vf (V @ target I)
Target LED Current (mA)
LED Temp (°C) & ΔVf (mV/°C)
ΔVf default ≈ -2 mV/°C
Resistor Preferences
Preferred Series
E12
E24
E96
Tolerance (%)
PWM Duty (%)
Resistor Power Options
1/8 W
1/4 W
1/2 W
1 W
2 W
Battery Estimate
Battery Type (capacity)
AA Alkaline (~2000 mAh)
AAA Alkaline (~1200 mAh)
CR2032 (~220 mAh)
9V Alkaline (~500 mAh)
Arduino/USB (N/A)
Custom…
Custom capacity (mAh)
Calculate
Reset
Export CSV
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