# How to calculate the power of the LED light strip?

author: Ivan Huang

2022-01-06

LED light strips are already one of the most popular LED products in the lighting market, and light strips are indispensable in almost all lighting projects. However, with so many products of light strips and various powers, some customers are wondering, what is the power of light strips? Is there a specific way to calculate it? Here, we will give you a good introduction to the power of the light strip.

**What is the power of the LED strip?**

The power of LED strips usually refers to the power of 1 meter of LED strips. Note that this is not a power of 5 meters, which will be described in detail later.

**Algorithm of the theoretical power of the strip**

Regarding the led strip, we can find that the general supplier quotes for 3528 60 lights and 120 lights are 4.8W/m and 9.6W/m, respectively, while the power of 5050 30 lights and 60 lights is written as 7.2W/m and 14.4W/m. So how are these powers calculated?

First of all, these are actually rated power and maximum power. The rated power is calculated according to the maximum current of the light strip. The specific algorithm is: rated power = voltage * rated current * number of lamp beads.

Let’s take 5050 led strip, 60 lights/m DC12V as an example to show you how to calculate it.

1) DC12V, usually 3 lights/group, so the number of groups per meter is 60/3=20 groups

2) The rated current of 5050 lamp beads is 60mA

3) Therefore, power = 12V*60mA*20=14.4W/m

Through the above calculation, we can know that the theoretical power of 5050 60 lights/meter DC12V light strip is 14.4W/meter.

First of all, these are actually rated power and maximum power. The rated power is calculated according to the maximum current of the light strip. The specific algorithm is: rated power = voltage * rated current * number of lamp beads.

Let’s take 5050 led strip, 60 lights/m DC12V as an example to show you how to calculate it.

1) DC12V, usually 3 lights/group, so the number of groups per meter is 60/3=20 groups

2) The rated current of 5050 lamp beads is 60mA

3) Therefore, power = 12V*60mA*20=14.4W/m

Through the above calculation, we can know that the theoretical power of 5050 60 lights/meter DC12V light strip is 14.4W/meter.

**Is the power the same for the same lamp beads and the same number of lamp beads?**

When you check the quotations of different suppliers, if it is the same lamp beads and the same number of lamp beads, you will find that the power is often the same. But, is this really the case?

Here, we take 2835 led strip, 120 lights/m as an example to calculate the power under different voltages.

1) 2835, 120 lights, 1 light/group, DC5V, power=5V*60mA*120=36W/M

2) 2835, 120 lights, 3 lights/group, DC12V, power=12V*60mA*(120/3)=28.8W/M

3) 2835, 120 lights, 6 lights/group, DC24V, power=24V*60mA*(120/6)=28.8W/M

4) 2835, 120 lights, 8 lights/group, DC24V, power=24V*60mA*(120/8)=21.6W/M

Through the above calculation, we can know that in the case of the same lamp bead, even with the same number of lamp beads, the power of the lamp beads may actually be different. Because it is used at rated current, the brightness of all lamp beads is the same, and the number of lamp beads is also the same, so theoretically, under the same rated power, the brightness is the same; and because the power is different, the luminous efficiency is also different. From the above calculation, it can be known that the luminous efficiency of the DC5V led strip is very low. If the brightness is required, try not to choose the DC5V solution.

**Does the rated power = the actual power of the light strip?**

The answer is negative.

1) The rated power refers to the maximum value of the current used in the light strip, so the rated power is actually the maximum power of the light strip. In the actual production process of the light strip, in order to ensure the long life and stable quality of the light strip, the power is generally lower than the actual one.

2) Excessive power is not conducive to heat dissipation

Through the above calculation, we can get that the theoretical power of the 2835 120 lamp led strip can reach 36W/M; if it is 2835 240 lamp 1 meter, it will reach 72W/m. Unless the circuit is wide and thick enough, and there is a large radiator to aid heat dissipation, otherwise the light strip will easily burn out due to overheating. So conventionally, the typical power of the 2835 120 lights/m led strip is controlled at 14.4W/m, so that the brightness is sufficient and the quality is stable.

Of course, the power can also be 22-24W/M according to customer needs, but it is recommended to use 0.5W/PCS 2835 lamp beads, 3OZ board, and cooperate with aluminum for heat dissipation.

**Can the power of the light strip be adjusted base on your request?**

Yes, under the circumstance that there will be no significant pressure reduction and sufficient heat dissipation, the power of the light strip can be adjusted at will under the rated power, and it can be customized according to the needs. Of course, custom-made products generally have MOQ, unless you have special requirements, please choose regular styles.

**How to control the power of the light strip?**

Through the above analysis, we know that the actual power of the light strip is often lower than the rated power of the light strip. Which method do we use to control the power of the light strip?

In fact, it is very simple. We only need to adjust the resistance of the light strip to control the power of the light strip.

In the actual production process, we can calculate the approximate resistance of the resistor. Resistance = (lamp with voltage-lamp bead voltage) / lamp bead current / resistance number

We still take 2835 120 lights 12V 14.4W/m, 3 lights 1 resistance light strip as an example, because the rated power is 28.8W, the actual power is only 14.4W, so we only use the general current of the lamp beads, which is 30mA; 2835 The Vf value of the lamp bead is 3V. So the resistance of the resistor=(12-3*3)/30/1=100 ohms

Through calculation, we know that the resistance of the resistor is about 100 ohms. So we can use the resistance of this resistance to make the sample and the power of the light strip, and then adjust the resistance appropriately to achieve the target power according to the actual power.

**Why is there a difference between the theoretical resistance and the actual resistance?**

1) The theoretical resistance value is calculated based on theory, and various parameters are required to be based on assumptions. Some parameters in the actual led strip control are different from the assumptions, mainly

2) The Vf value of the lamp bead is not 3V. Regarding the Vf value of 2835, the conventional 0.2W lamp bead is 3-3.1V, and the large-size chip can achieve 2.8V-3V. Because we only use the 30mA half of the lamp beads, the Vf value is usually only about 2.9V under this current situation.

3) The circuit board of the light strip has impedance, which is what we call voltage drop

**Is the power of each batch of light strips the same?**

Yes, with the same configuration, the power of each batch of light strips is in a stable power range, generally plus or minus 10% is a more suitable power range. This is because the Vf value of the lamp bead is also a range. In addition, the resistance used in the lamp strip is usually plus or minus 5% resistance, so it is normal for the power of each batch to fluctuate, but they are all within the same range.

**Why do you want to advertise the power of the light strip according to the power of 1 meter?**

1) A conventional measurement method in this market is generally accepted by the market

2) There are strict requirements for the integrating sphere to test the brightness of the lamp. The 1 meter lamp strip is attached to the aluminum material to easily test various parameters including power and produce a test report.

3) If a roll of 5 meters is used, the tested data is often incorrect

**If the power of a 1 meter led strip is 14.4W, then is a 5 meter/roll led strip 14.4*5=72W/roll?**

1) First of all, the market generally advertises in this way, which is easier for consumers to accept

2) In fact, this algorithm is wrong. Because of the pressure drop, when the light strip is connected to 5 meters, the power of 5 meters will be far less than the power of 1 meter * 5 power.

3) So, if you find that the power of a 5m roll of light strip is different from the power of 1m*5, please don’t be surprised, this is normal imagination

The above is about how to calculate the power of LED strips. Have you learned it?

If you still don’t understand, please feel free to contact us. We have been making light strips for 13 years, and we have enough experience to share with you.