Lumens to Watts Calculator

You can use our lumens to watts calculator to calculate the efficiency of different bulbs and low wattage LEDs based on their brightness to power ratio, known as luminous efficacy, where the brightness of the light is in lumens and its power, in wattage.

You can then compare your LED bulb wattage with other light bulbs to observe how much electricity you'll save. Omni's electricity cost calculator will make the task even easier. And to further reduce your electricity bill, you may try our outstanding appliance wattage calculator.

Furthermore, we will tell you how to calculate lumens to watts using a formula and show you a comparison chart of LED wattage consumption against other bulbs.

• We can use this lumens to watts calculator to find the required LED bulb wattage, i.e., the power needed for our light bulb to produce the specified amount of visible light, based on its luminous efficacy.

• You can also use it to find the luminous flux, i.e., the brightness of light that our bulb produces with a given amount of power and luminous efficacy.

• Finally, we can find the luminous efficacy, i.e., how efficiently our light bulb produces visible light based on its power to Lumen ratio.

Here's how we use the lumens to wattage calculator for LED lights.

1. Enter the luminous efficacy of your light source. The default is at 100 lm/W, primarily for LEDs.

2. Enter the brightness of your LED in lumens or nits, e.g., 1200 lumens or 350.25 nits. It is usually mentioned on the packaging of the bulb or you know the lumens of the old bulb you want to replace.

3. Once you have entered your bulbs luminous efficacy and brightness, you'll determine how much power or wattage your light source requires.

   Thus, with a luminous efficacy of 100 lm/W, for producing 1200 lumens, the required power is 12 watts.

The following table shows a range of luminous efficacies for different light bulbs:

Because different manufacturers have different standards, there are variations in lumens to watts ratio for the same light sources.

You can also try our lighting calculator to determine how much lighting you'll require based on the dimensions of your surface.

Based on their brightness and efficiency, we use the following formula when we want to find the required wattage of our low-wattage LED bulbs:

where:

• $P$ – Power required, in watts;
• $\varPhi _{V}$ – Luminous flux or the brightness in lumens (lm); and
• $\eta$ – Luminous efficacy or the efficiency of producing visible light in lumens per watt (lm/W).

As an example, let's find the required wattage of an LED that has a luminous efficacy of 120 lm/W, and produces 1200 lumens:

1. Placing the values in the formula, we get:

   $P _{(\text W)} = 1200 / 120 = 10$

2. Thus, our LED requires 10 watts for producing 1200 lumens.

Let's take another example where we wish to find the luminous efficacy of our bulb, which consumes 15 watts and produces 1000 lumens:

1. In order to find its luminous efficacy, we rearrange the formula as follows:

   $\eta _{(\text{lm/W})} = \varPhi _{V (\text{lm})} / P _{(\text W)}$

2. Placing the values in the formula, we get:

   $\eta = 1000 / 15$

3. Thus, our bulb's luminous efficacy is 66.67 lm/W.

Here's an LED wattage chart comparing a low-wattage LED bulb of 12 W at 100 lm/W against other bulb types with different luminous efficacies.