RGB LED Resistor Calculator
This RGB LED Resistor Calculator calculates separate resistor values, current, power, and wiring guidance for red, green, and blue LED channels.
RGB LEDs contain three separate LED dies, so each channel normally needs its own current-limiting resistor. The calculator supports common-cathode, common-anode, and independent-channel wiring.
Engineering tool
RGB LED Resistor Calculator
Calculate separate red, green, and blue channel resistors, current, power, total load, wiring guidance, and approximate RGB preview.
Voltage feeding the RGB LED channels.
This changes wiring guidance. Resistor calculations remain per channel.
Red LED forward voltage.
Red target current.
Green LED forward voltage.
Green target current.
Blue LED forward voltage.
Blue target current.
Total RGB current
60 mA
Result console
- Total RGB current
- 60mA
- Total LED power
- 160mW
- Total resistor power
- 140mW
- Total supply power
- 300mW
- Overall efficiency
- 53.333333%
- Resistors required
- 3resistors
Red Channel
Result console
- Exact resistance
- 150Ω
- Recommended standard resistance
- 150Ω
- Actual current
- 20mA
- Resistor power
- 60mW
- Recommended resistor rating
- 0.25W
- LED power
- 40mW
- Channel efficiency
- 40%
Green Channel
Result console
- Exact resistance
- 100Ω
- Recommended standard resistance
- 100Ω
- Actual current
- 20mA
- Resistor power
- 40mW
- Recommended resistor rating
- 0.25W
- LED power
- 60mW
- Channel efficiency
- 60%
Blue Channel
Result console
- Exact resistance
- 100Ω
- Recommended standard resistance
- 100Ω
- Actual current
- 20mA
- Resistor power
- 40mW
- Recommended resistor rating
- 0.25W
- LED power
- 60mW
- Channel efficiency
- 60%
RGB Preview
The color preview is an approximate visual indicator and does not represent calibrated LED chromaticity, luminous intensity, spectral output or perceived brightness.
Wiring Summary
Common cathode connects to ground. Red, green, and blue anodes each connect to the supply or driver through their own resistor.
Each red, green, and blue channel requires its own resistor. Never use one shared resistor for all three channels.
Equal electrical current does not guarantee equal perceived brightness because RGB dies have different luminous efficiency and human-eye sensitivity.
Formula reference
RGB LED Resistor Formulas
Apply the channel equations independently to red, green, and blue. The calculator converts engineering units before selecting standard values.
Rexact = (Vs - Vf) / IfRselected = next higher preferred resistor valueIactual = (Vs - Vf) / RselectedPresistor = Iactual² × RselectedPLED = Vf × IactualPsupply = Vs × IactualEfficiency = PLED / Psupply × 100%Itotal = IR + IG + IBPLEDtotal = PLEDR + PLEDG + PLEDBPresistorTotal = PR + PG + PBPsupplyTotal = Vs × ItotalVariable definitions
- Vs
- Supply voltage
- Vf
- Forward voltage of one RGB channel
- If
- Target or actual channel current
- Rselected
- Recommended standard resistor value
- PLED
- LED channel power
- Presistor
- Resistor dissipation
Variable Definitions
- Red, green and blue dies
- Separate LED chips inside the RGB package, each with its own electrical behavior.
- Common cathode
- A wiring style where the RGB LED shares the cathode connection.
- Common anode
- A wiring style where the RGB LED shares the anode connection and usually uses active-low control.
- Channel resistor
- A separate current-limiting resistor for one RGB color channel.
- Current mismatch
- The maximum difference between enabled RGB channel currents.
- RGB preview
- A normalized current-based preview, not a calibrated color measurement.
How to Use
1. Select LED type
Choose common cathode, common anode, or independent channels for wiring guidance.
2. Enter each channel
Use separate forward voltage, current, or resistor values for red, green, and blue.
3. Check totals
Review total current, resistor power, RGB preview, and microcontroller drive warnings.
Worked Examples
Calculate RGB Resistors
With a 5 V common-cathode RGB LED at 20 mA per channel, red needs 150 Ω while green and blue need 100 Ω.
- Red resistor
- 150 Ω
- Green resistor
- 100 Ω
- Blue resistor
- 100 Ω
- Red resistor power
- 60 mW
- Green resistor power
- 40 mW
- Blue resistor power
- 40 mW
- Total current
- 60 mA
- Total LED power
- 160 mW
- Total resistor power
- 140 mW
- Total supply power
- 300 mW
- Overall efficiency
- 53.33%
Incorrect Equal Resistors
If red, green, and blue all use 150 Ω, red draws more current because its forward voltage is lower.
- Red current
- 20.00 mA
- Green current
- 13.33 mA
- Blue current
- 13.33 mA
Three separate dies
RGB LEDs contain separate red, green, and blue LED dies inside one package.
Red voltage is often lower
Red forward voltage is usually lower than green and blue, but exact values are device-dependent.
Use one resistor per channel
Each color channel needs its own current-limiting resistor.
Equal current is not equal brightness
Perceived brightness depends on luminous intensity, wavelength, binning, optics, and eye sensitivity.
PWM is common
PWM is often used for RGB dimming, color mixing, and animation.
Check GPIO limits
Microcontroller GPIO current limits must be checked; drivers may be required for higher current.
Common-anode polarity differs
Common-anode RGB LEDs often require active-low control logic.
Forward voltage changes
Forward voltage changes with current and temperature, affecting color balance.
Common Mistakes
- Using one resistor for all RGB channels.
- Using the same resistor value without checking each forward voltage.
- Assuming equal current produces equal brightness.
- Ignoring microcontroller GPIO current limits.
- Connecting common-anode and common-cathode LEDs incorrectly.
- Forgetting active-low behavior for common-anode RGB LEDs.
- Ignoring resistor power dissipation.
- Driving high-current RGB LEDs directly from GPIO pins.
- Treating the visual preview as a calibrated color result.
Support reference
FAQ
Why does each RGB LED channel need its own resistor?
Red, green, and blue dies have different forward voltages. One shared resistor can cause unequal current and unstable color balance.
What is the difference between common anode and common cathode RGB LEDs?
A common-cathode RGB LED shares the cathode connection, while a common-anode RGB LED shares the anode connection and is often controlled active-low.
Can I use the same resistor for red, green and blue?
Only after calculation. Equal resistor values often produce unequal current because each color channel has a different forward voltage.
Does equal RGB current mean equal brightness?
No. Perceived brightness depends on LED luminous intensity, wavelength, binning, optics, and human-eye sensitivity.
When should RGB LEDs use PWM?
PWM is commonly used when a controller needs adjustable color mixing, dimming, animation, or brightness calibration.
Can a microcontroller pin drive an RGB LED directly?
Only if each GPIO pin current and package total current stay within datasheet limits. Higher current requires transistor or MOSFET drivers.
Documentation
Related Engineering Guides
Design notes, guides, and engineering articles linked to this tool.
Engineering Guide
Understanding LEDs
Learn LED fundamentals including forward voltage, forward current, wavelength, color, luminous intensity, LED types, packages, current limiting, and thermal design.
14 min · Beginner
Engineering Guide
How to Choose the Right LED
Choose LEDs by application, forward voltage, current, brightness, wavelength, CCT, viewing angle, package, power, thermal behavior, and datasheet limits.
15 min · Intermediate
Engineering Blog
10 Common LED Design Mistakes (and How to Avoid Them)
Avoid LED design mistakes involving current limiting, resistor value, forward-voltage variation, excessive current, resistor power, parallel branches, polarity, brightness, thermal design, and color selection.
14 min · Intermediate
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Engineering Disclaimer
This calculator provides first-order estimates for RGB LED resistor sizing. Verify RGB LED datasheets, microcontroller current limits, resistor derating, thermal behavior, color requirements, and driver polarity before production use.