Yageo high-volume chip resistors
Good fit for standard LED current-limiting resistor values in common SMD packages.
LED resistor toolVoltage headroom OK
LED Series Resistor Calculator
Calculate the right current-limiting resistor for a single LED or LED string from supply voltage, forward voltage, and target current.
Enter supply voltage, LED forward voltage, target current, and LED count to size the current-limiting resistor.
Circuit reference
Size the LED current-limiting resistor
LED string inputs
Set the supply, forward voltage, current target, and number of LEDs in series to estimate the resistor value and power.
Calculated output
Voltage headroom OKRecommended resistor
330 Ohm
The standard E-series resistor 330 Ohm is recommended, resulting in an operating current of 18.18 mA. Confirm resistor wattage and LED forward-voltage spread before release.
Calculated resistor
300 Ohm
Resistor power
109.1 mW
Total LED drop
6 V
LED current
18.18 mA
Need components for your project? Search parts & check stock instantly.
Move from LED math to real resistor sourcing
Use the calculated resistor and power rating to search stocked parts or escalate into RFQ workflows.
Suggested query
330 Ohm resistor 218.2 mW
Lighting BOM workflow
Need to source the whole LED drive path?
Move beyond a single resistor when you need LED, driver, and supporting passives quoted together.
0402-2512
Vishay pulse / power resistors
Useful when LED strings need higher pulse tolerance or more thermal margin.
Bourns thick-film power parts
Helpful for higher-voltage indicator circuits and industrial LED panels.
LED resistor reference
How to calculate an LED series resistor
An LED series resistor calculator estimates the resistor needed to limit current through an LED or LED string. It is one of the most common beginner and prototype calculations in electronics.
The resistor absorbs the difference between the supply voltage and the total LED forward voltage at the desired current. After the value is calculated, the next engineering step is checking resistor power dissipation and choosing the nearest stocked standard value.
LED resistor formula and unit conversion
Core formula
R = \\frac{V_{supply} - nV_f}{I}
| Supply | LED string | Typical resistor |
|---|---|---|
| 5 V | 1 x 2.0 V red LED at 20 mA | 150 Ohm |
| 12 V | 3 x 2.0 V red LEDs at 20 mA | 300 Ohm |
| 24 V | 6 x 3.0 V white LEDs at 20 mA | 300 Ohm |
FAQ
Frequently asked questions about LED series resistors
Can I use one resistor for several LEDs?
Yes, if the LEDs are in series and the supply voltage is high enough to support the total forward voltage plus resistor headroom.
Why should I choose a standard resistor above the calculated minimum?
A slightly larger standard value often gives safer current and better thermal margin when supply or forward voltage varies.
Do I still need to check resistor wattage after calculating the value?
Yes. The resistance value alone is not enough; the part must also survive the power it dissipates in operation.