LED Resistor Calculator

Your details

In series, all LEDs share one resistor and the same current. In parallel, each LED ideally has its own resistor; this calculator handles equal parallel branches.
How many LEDs in your circuit. For series: all LEDs in one chain. For parallel: number of identical parallel branches.
LEDs
The voltage of your power source. Common values: 3.3 V (microcontroller I/O), 5 V (USB/Arduino), 9 V (battery), 12 V (automotive/LED strip).
V
Selects a typical forward voltage for that color. Use Custom if you have the actual Vf from your datasheet.
The voltage drop across one LED at its rated current. Find this in your LED datasheet. Typical values: 1.8-2.2 V for red/yellow/green, 3.0-3.4 V for blue/white.
V
The desired forward current through each LED. Standard indicator LEDs run at 10-20 mA. High-brightness types may spec 30+ mA. When in doubt, use 20 mA.
mA
Resistor valueValid resistor value
160Ohm

Exact calculated resistance needed

Nearest E12 standard value150 Ohm
Nearest E24 standard value160 Ohm
Power in resistor64.0 mW
Minimum resistor wattage250 mW minimum
Power per LED36.0 mW
Total LED power36.0 mW
Total circuit power100.0 mW
Resistance (Ohm)160

You need a 150 Ohm resistor.

  • Buy a 150 Ohm resistor (nearest E12 standard) - it is safe for this circuit and widely available at electronics suppliers.
  • Use a resistor rated at 250 mW or higher to prevent overheating. At very low duty cycles (PWM dimming), a lower-rated part may be acceptable.
  • The E24 value (160 Ohm) is slightly closer to the exact resistance and delivers current closer to your target. Use it if your supplier stocks 5% parts.

Next stepAfter wiring, measure the actual LED current with a multimeter in series. Adjust the resistor value if the measured current differs from your target by more than 10%.

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