A FREE LED Resistor Calculator is an online tool that helps you determine the correct resistor value needed to safely connect an LED to a power source.
I=VRI = \frac{V}{R}
I=12.0 V6.0 Ω=2.00 AI=\frac{\text{12.0}\,\mathrm{V}}{\text{6.0}\,\Omega}=\text{2.00}\,\mathrm{A}I=6.0Ω12.0V=2.00A
VsV_sVs
V
VsV_sVs
RRR
Ω
RRRVs = 12.0 V+-R = 6.0 ΩI = 2.00 A
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What does an LED Resistor Calculator do?
An LED normally should not be connected directly to a battery or power supply because excessive current can damage the LED. The calculator determines the resistor needed to limit the current to a safe level.
The basic calculation is:
R = (Vs − Vf) / I
Where:
- R = required resistor resistance in ohms (Ω)
- Vs = supply voltage
- Vf = LED forward voltage
- I = desired LED current in amperes
Example
Suppose you have:
- Supply voltage: 12 V
- LED forward voltage: 2 V
- Desired current: 20 mA (0.020 A)
The required resistance is:
R = (12 − 2) / 0.020 = 500 Ω
A standard resistor value such as 510 Ω would typically be selected.
What can you enter?
A good LED Resistor Calculator can include:
- Supply voltage
- LED forward voltage
- LED current
- Number of LEDs
- Resistor value
- Resistor power rating
- LED color/type
- Series or parallel configuration
Who is it useful for?
This free tool is useful for:
- Electronics beginners
- Arduino projects
- Raspberry Pi projects
- DIY LED lighting
- Electronic circuit design
- Automotive LED projects
- Hobbyists
- Students
- Engineers and technicians
In simple terms: a FREE LED Resistor Calculator tells you what resistor to use with an LED so the LED receives a safe amount of current.
