LED Current Calculator

You just have to enter the Forward Voltage rating of the LED, and the Lumen of the LED, and the calculator will quickly calculate and give you the Current or the Ampere rating of the LED.

Led Current Calculator Using Voltage, Lumen, And Efficacy

Now in this first calculator what we do is we try to find the actual current rating of one led based on its voltage drop and its total lumen output.

We know that how much current one led will consume that is always based on how much watt it needs to produce that much brightness, and we also know that how much brightness is equal to how much power, right?

So we use one quantity called luminous efficacy, that tells us how much lumens the led will produce for every 1 watt it consumes.

Now if we already know the led forward voltage and we know how many lumens it is producing, then we can select one luminous efficacy from the dropdown list.

That value is normally decided based on the led color and quality. For example if we are using one white smd led then we can use around 130 lm/w, if it is one older led or warm white one then we can select 90 or 60 lm/w.

If it is color led like red or blue then we can go with 30 lm/w. This dropdown is already given, so user can choose according to his led type.

Now when we enter the voltage and lumen and select efficacy then the calculator will first calculate how much watts the led is using, that is done by:

Watts = lumen / efficacy

After that we find the current using:

Current = watts / voltage

That is how we can estimate the actual operating current of one led from its lumen and voltage. Output result is shown in amps and also in milliamp.

So this tool is very helpful when we don’t know the current rating but we know the brightness and voltage. That helps to estimate safe current for led driver or resistor.

LED Power And Efficacy Calculator Using Voltage, Current, And Optional Lumen

In this second calculator we do something reverse. That means here we already know the led forward voltage and also the operating current, because these two values are normally mentioned in any led datasheet.

From these two we can directly find how much watt that led is consuming. This we do using:

Power = voltage × current

So we get exact watt value and this tells us how much power this led is consuming.

But now if we also know the lumen output of that led, like from datasheet or manufacturer info, then we can also find how much efficient that led is. That means how many lumens per watt it is producing. That is called luminous efficacy and it is calculated using:

Efficacy = lumen / power

In this way we can estimate how good or how efficient our led is. If we get the efficacy above 120 lm/w then it is high quality led. If it is around 80 or less then it is lower type.

In this tool lumen is optional so even if user does not know it still he can calculate wattage of led from voltage and current.

This helps when we are designing led driver or we are testing led rating using multimeter, and we want to check how much power it is using and whether it is efficient or not.