# LED Resistor Calculator Online

This series LED resistor calculator comes handy when you have a single LED of the same color or different color of LEDs and need to know which resistor you should use. This calculator will give you the value of series LED resistance that could be used in series with an LED to prevent it from damaging due to over current.

One of the features of this calculator is that it will also give you power dissipation due to LED as well as resistor. Also suggests the Standard Value of Resistor according to E3, E6, E12, E24, so that you can directly use the nearest available standard resistors.

To use this calculator, enter three known values (Vs, Vf, If) and press “Calculate” to solve for the others.

### LED Resistor Calculator

Check Typical forward **LED Voltage (Vf) calculator** for different colors Here !!

You can directly check most commonly used **LED Resistor Value **for different battery/ cells**.**

Power Dissipation is calculated considering the actual calculated value of ‘R’. When using the standard value of resistor, consider the selected value for Power Dissipation calculation.

PL = Vf x If <for LED>

PR = R x I^2 <for Resistor>

To calculate the resistor value manually or theoretically, needed for a simple LED circuit, apply Ohm’s Law, then substitute parameters.

V = I x R —<ohm’s law>

Vs = Vr + Vf —<total voltage drop>

Vs = Ir.R + Vf —<Vr = Ir.R>

Ir.R = Vs – Vf —<adjusting the eq.>

R = (Vs – Vf )/Ir —<we know that Ir= If >

R = (Vs – Vf )/If —<final result>

So the equations…

where:

- VS is the source voltage, measured in volts (V),
- Vf is the forward voltage across the LED, measured in volts (V),
- Ir = the the current through the Resistor*, measured in Ampere (A), and
- If = the current through the LED*, measured in Ampere (A), and
- Rs = R is the current limiting series resistor, measured in Ohms (Ω).

* All the components are in series, thus the current through the circuit will be the same. Therefore, “If = Ir” = the current through the Resistor = the current through LED

This calculator is a fundamental application of Ohm’s Law Calculations, adding the consideration of the voltage drop from the LED.