LED resistor for 3.3 V
Resistor values for LEDs on ESP32, Raspberry Pi and other 3.3 V logic, or a 3.3 V regulator rail. 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 3.3 V — change the LED or current to suit your part.
3.3 V LED resistor table at 20 mA
20 mA is the classic rating for 3 mm and 5 mm indicator LEDs. Formula: R = (3.3 − Vf) ÷ 0.020.
| LED color | Vf | Exact | E12 (up) | E24 (up) | Actual current | Power → rating |
|---|---|---|---|---|---|---|
| Red / orange | 2 V | 65 Ω | 68 Ω | 68 Ω | 19.1 mA | 25 mW → 1/8 W |
| Yellow | 2.1 V | 60 Ω | 68 Ω | 62 Ω | 19.4 mA | 23 mW → 1/8 W |
| Green (traditional) | 2.2 V | 55 Ω | 56 Ω | 56 Ω | 19.6 mA | 22 mW → 1/8 W |
| True green (unreliable: only 0.3 V headroom) | 3 V | 15 Ω | 15 Ω | 15 Ω | 20 mA | 6 mW → 1/8 W |
| Blue / white (unreliable: only 0.1 V headroom) | 3.2 V | 5 Ω | 5.6 Ω | 5.1 Ω | 19.6 mA | 2 mW → 1/8 W |
3.3 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 | 130 Ω | 150 Ω | 130 Ω | 10 mA | 13 mW → 1/8 W |
| Yellow | 2.1 V | 120 Ω | 120 Ω | 120 Ω | 10 mA | 12 mW → 1/8 W |
| Green (traditional) | 2.2 V | 110 Ω | 120 Ω | 110 Ω | 10 mA | 11 mW → 1/8 W |
| True green (unreliable: only 0.3 V headroom) | 3 V | 30 Ω | 33 Ω | 30 Ω | 10 mA | 3 mW → 1/8 W |
| Blue / white (unreliable: only 0.1 V headroom) | 3.2 V | 10 Ω | 10 Ω | 10 Ω | 10 mA | 1 mW → 1/8 W |
LEDs in series on 3.3 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 | 1 | 2 V | 68 Ω (25 mW) | 61% |
| Yellow | 1 | 2.1 V | 62 Ω (23 mW) | 64% |
| Green (traditional) | 1 | 2.2 V | 56 Ω (22 mW) | 67% |
| True green | 0 | Less than 1 V headroom — use a higher supply | ||
| Blue / white | 0 | Less than 1 V headroom — use a higher supply | ||
When the supply is not exactly 3.3 V
Current with the 20 mA resistor from the table above (68 Ω for red) at the voltages this supply really sees:
| Condition | Supply | Red LED |
|---|---|---|
| GPIO pin sagging under load | 3 V | 14.7 mA |
| Nominal | 3.3 V | 19.1 mA |
| Upper limit for 3.3 V logic | 3.6 V | 23.5 mA |
Notes for 3.3 V circuits
3.3 V is the awkward supply for LEDs. A red, orange or yellow LED leaves about 1.2 V across the resistor, which is enough for a stable current. A blue, white or true-green LED leaves only 0.1–0.3 V, and the real forward voltage of those LEDs spreads from roughly 2.8 V to 3.4 V, so the same resistor can give a bright LED, a dim LED or no light at all. The table marks those rows as unreliable. If you need a white or blue LED on a 3.3 V board, power it from 5 V and switch it with a transistor, or use a constant-current LED driver.
GPIO pins add their own limit. Raspberry Pi pins are usually kept to 16 mA each and around 50 mA for all pins together, and a pin's output voltage sags below 3.3 V as it sources current. For indicator LEDs on a Pi or ESP32, 2–5 mA is plenty bright with modern parts — use the 10 mA table as an upper bound, or simply a 1 kΩ resistor with a red LED (about 1.3 mA).
Other supplies: 5 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 3.3 V?
For a red LED (≈2 V) at 20 mA: (3.3 − 2) ÷ 0.02 = 65 Ω, so use 68 Ω. At 10 mA a red LED needs 130 Ω.
What wattage resistor for an LED on 3.3 V?
A red LED at 20 mA puts 25 mW into a 68 Ω resistor, so use 1/8 W or larger (twice the dissipated power).
How many LEDs can I run in series on 3.3 V?
Leaving at least 1 V for the resistor: 1 × red / orange, 1 × yellow, 1 × green (traditional), 0 × true green, 0 × blue / white.
Can I connect an LED to 3.3 V without a resistor?
No. Even when the LED voltage is close to 3.3 V, nothing limits the current except the pin or regulator. Always use a series resistor; for a red LED, 68–150 Ω for 10–20 mA, or 1 kΩ for a dim indicator.