LED resistor for 5 V
Resistor values for LEDs on USB power, Arduino Uno/Nano pins and 5 V regulator rails. The tables use typical forward voltages and round up to the next standard value, so the LED never gets more current than the target. The calculator is preset to 5 V — change the LED or current to suit your part.
5 V LED resistor table at 20 mA
20 mA is the classic rating for 3 mm and 5 mm indicator LEDs. Formula: R = (5 − Vf) ÷ 0.020.
| LED color | Vf | Exact | E12 (up) | E24 (up) | Actual current | Power → rating |
|---|---|---|---|---|---|---|
| Red / orange | 2 V | 150 Ω | 150 Ω | 150 Ω | 20 mA | 60 mW → 1/8 W |
| Yellow | 2.1 V | 145 Ω | 150 Ω | 150 Ω | 19.3 mA | 56 mW → 1/8 W |
| Green (traditional) | 2.2 V | 140 Ω | 150 Ω | 150 Ω | 18.7 mA | 52 mW → 1/8 W |
| True green | 3 V | 100 Ω | 100 Ω | 100 Ω | 20 mA | 40 mW → 1/8 W |
| Blue / white | 3.2 V | 90 Ω | 100 Ω | 91 Ω | 19.8 mA | 36 mW → 1/8 W |
5 V LED resistor table at 10 mA
Modern LEDs are bright at 10 mA or less, and half the current doubles the resistor value and halves its heat.
| LED color | Vf | Exact | E12 (up) | E24 (up) | Actual current | Power → rating |
|---|---|---|---|---|---|---|
| Red / orange | 2 V | 300 Ω | 330 Ω | 300 Ω | 10 mA | 30 mW → 1/8 W |
| Yellow | 2.1 V | 290 Ω | 330 Ω | 300 Ω | 9.67 mA | 28 mW → 1/8 W |
| Green (traditional) | 2.2 V | 280 Ω | 330 Ω | 300 Ω | 9.33 mA | 26 mW → 1/8 W |
| True green | 3 V | 200 Ω | 220 Ω | 200 Ω | 10 mA | 20 mW → 1/8 W |
| Blue / white | 3.2 V | 180 Ω | 180 Ω | 180 Ω | 10 mA | 18 mW → 1/8 W |
LEDs in series on 5 V
The most LEDs one resistor can serve while still leaving at least 1 V across it (so the current stays predictable), with the resistor for 20 mA. Efficiency is the share of supply power that reaches the LEDs.
| LED color | Max in series | LED voltage | Resistor (power) | Efficiency |
|---|---|---|---|---|
| Red / orange | 2 | 4 V | 51 Ω (20 mW) | 80% |
| Yellow | 1 | 2.1 V | 150 Ω (56 mW) | 42% |
| Green (traditional) | 1 | 2.2 V | 150 Ω (52 mW) | 44% |
| True green | 1 | 3 V | 100 Ω (40 mW) | 60% |
| Blue / white | 1 | 3.2 V | 91 Ω (36 mW) | 64% |
When the supply is not exactly 5 V
Current with the 20 mA resistor from the table above (150 Ω for red, 91 Ω for white) at the voltages this supply really sees:
| Condition | Supply | Red LED | White LED |
|---|---|---|---|
| USB low limit (−5%) | 4.75 V | 18.3 mA | 17 mA |
| Nominal | 5 V | 20 mA | 19.8 mA |
| USB high limit (+5%) | 5.25 V | 21.7 mA | 22.5 mA |
Notes for 5 V circuits
5 V is the friendliest LED supply: every common color leaves at least 1.8 V across the resistor, so the current stays stable even if the forward voltage of your particular LED differs from the typical value. Two red or yellow LEDs also fit in series (4.0–4.2 V), but blue and white LEDs must be one per resistor.
On an Arduino Uno or Nano (ATmega328P), the absolute maximum is 40 mA per I/O pin and 200 mA for the whole chip; the datasheet specifies the output levels at 20 mA, which is the practical ceiling. Driving several LEDs at 20 mA each quickly adds up, so the 10 mA column is the better default for indicator LEDs on a microcontroller. USB ports allow the 5 V rail to vary by ±5%, which the supply-variation table below shows has little effect at this headroom.
Other supplies: 3.3 V · 9 V · 12 V · 24 V. The method and edge cases are explained in the LED resistor guide, and wattage in resistor power ratings.
FAQ
What resistor do I need for an LED on 5 V?
For a red LED (≈2 V) at 20 mA: (5 − 2) ÷ 0.02 = 150 Ω, so use 150 Ω. For a blue or white LED (≈3.2 V) at 20 mA: 90 Ω, so 91 Ω. At 10 mA a red LED needs 300 Ω.
What wattage resistor for an LED on 5 V?
A red LED at 20 mA puts 60 mW into a 150 Ω resistor, so use 1/8 W or larger (twice the dissipated power).
How many LEDs can I run in series on 5 V?
Leaving at least 1 V for the resistor: 2 × red / orange, 1 × yellow, 1 × green (traditional), 1 × true green, 1 × blue / white.
What resistor for an LED on an Arduino pin?
For a red LED, 150 Ω gives about 20 mA and 330 Ω about 9 mA. 220 Ω (about 14 mA) is the usual compromise. For blue or white LEDs, 100 Ω gives about 18 mA and 220 Ω about 8 mA.