LED Resistor Calculator

From the LED datasheet at the current you intend to run - typically 1.8-2.2 V for red, 3.0-3.4 V for blue and white.
0.02 A is 20 mA, the usual rating for a 5 mm indicator LED. Check the datasheet.
Resistance needed
150.000 ohm
LED Resistor Calculator
Power in the resistor
0.0600 W
Voltage across the resistor
3.0000 V
Nearest preferred value (rounded up)
150.00 ohm
Current with that preferred value
0.020000 A
Power in the LEDs
0.0400 W
Total power drawn
0.1000 W
Suggested resistor rating
0.125 W
Worked out from Ohm's law applied to the series resistor: R = (Vs - Vf) / I, P = (Vs - Vf) x I and 2 other sources.

How this is worked out

5 steps
  1. 1 LED(s) at 2 V each drop 2 V.
  2. Voltage left for the resistor = 5 - 2 = 3 V.
  3. R = 3 / 0.02 = 150 ohm.
  4. P = 3 x 0.02 = 0.06 W.
  5. Nearest E24 value at or above that: 150 ohm, giving 0.02 A.

Results are general information, not financial, tax, legal, medical or engineering advice.