LED resistor values for common supplies and colors

These values come from the same formula as the LED Resistor calculator: R = (Vs − n·Vf) / I, rounded up to the next E24 (5%) value so the LED current stays at or below the target. Each "open" link loads the calculator with those inputs, so you can change the forward voltage to match your datasheet.

Assumed forward voltages

Forward voltage depends on the exact LED, its current and temperature. These are typical values for standard 3 mm and 5 mm indicator LEDs at about 20 mA. Use the datasheet value when you have it.

"Green" LEDs made with InGaN (bright or "true" green) have a Vf close to blue, about 3.0 to 3.2 V. For those, use the blue row or enter your own value.

How to read the table

• Exact R: the calculated resistance before rounding.
• E24 (rounded up): the next standard 5% value at or above the exact value.
• Actual current: the LED current with the E24 resistor and the assumed Vf.
• Resistor power: I² · R with the E24 resistor.
• Rating (2× margin): the smallest common rating (0.125, 0.25, 0.5, 1, 2 W) that is at least twice the resistor power. This is the rating the calculator suggests.
• Suggested package: a common SMD size and a through-hole size that usually meet that rating. Power ratings for a given package differ between manufacturers (for example, some 0805 parts are rated 0.125 W and others 0.25 W), so check the datasheet. Typical: 0805 at 0.125 W, 1206 at 0.25 W, 2010 at 0.5 W, 2512 at 1 W.

One LED at 20 mA

One LED at 10 mA, 3.3 V and 5 V

Many modern indicator LEDs are clearly visible at 10 mA or less, and 3.3 V microcontroller pins often should not source 20 mA. Check the pin current limit in your microcontroller datasheet.

3.3 V

5 V

LEDs in series at 12 V and 24 V

Putting LEDs in series uses the supply more efficiently, because less voltage is wasted in the resistor. Leave at least about 1 to 2 V across the resistor so the current stays stable when Vf varies.

Notes

1. Values are for the assumed Vf above. If your LED's Vf is different, open the row's link and change "LED forward voltage". With high supply voltages (12 V, 24 V) a small Vf difference barely changes the result. With low supply voltages it matters a lot.
2. Blue and white LEDs on 3.3 V. Only 0.2 V is left across the resistor, so the current depends almost entirely on the LED's actual Vf. With the 10 Ω resistor from the 20 mA table, an LED with Vf = 3.0 V draws 30 mA, and one with Vf = 3.2 V draws 10 mA. With the 20 Ω resistor from the 10 mA table, the same LEDs draw 15 mA and 5 mA. Some LEDs will barely light at all. Use a 5 V supply, a constant-current driver, or a lower-Vf color.
3. 9 V and above with 20 mA: the suggested rating is 0.5 W or more in most rows. A common 1/4 W through-hole resistor is not enough there.
4. Supply tolerance. A "12 V" supply may be 11.4 to 12.6 V, and a 12 V lead-acid battery can reach 14.4 V while charging. Open the link and enter the highest voltage to check the maximum current and power.
5. Not for high-power LEDs. For LEDs above about 0.5 W, or for LED strips, use a constant-current driver or follow the strip maker's instructions.

Share-link format

The calculator stores its inputs in the page URL. Any result can be opened directly with:

https://ohmlark.com/calculators/led-resistor?vs=<supply V>&vf=<forward voltage V>&if=<current mA>&n=<LEDs in series>&series=<E12|E24|E96>

Example: https://ohmlark.com/calculators/led-resistor?vs=12&vf=3.1&if=20&n=1&series=E24 opens 12 V, one white LED at 20 mA, and shows 470 Ω (E24) and 168.5 mW.

Values may be typed with units or prefixes as in the calculator (for example if=0.02A or if=20mA). Unknown keys are ignored, series must be E12, E24 or E96, and any key left out uses the default (5 V, 2.0 V, 20 mA, 1 LED, E24).