How to calculate power for led strip lights?

At SuperLightingLED we size the power supply for every LED strip project the same way: watts per meter × length, plus headroom. Enter your numbers below, check the reference figures, then follow the 4-step example with our 24V RGB LED neon.

LED strip power calculator

Find the watts per meter on the product page (see Step 1 below), enter the length in meters or feet and choose the strip voltage. The calculator gives the total power, the power supply size and the current.

Why 50 W and not 48 W? Dividing by 0.8 is the same as multiplying by 1.25, the headroom our power supply sizing diagram (B3) uses. The worked example below multiplies by 1.2, which gives a slightly lower figure (40 W becomes 48 W instead of 50 W). Either way, when there is no exact size, choose the next power supply up.

The amps tell you which controller and cable to use: 60 W at 12 V is 5 A, the same 60 W at 24 V is 2.5 A. For the cable size, see our wire gauge vs run length chart (B5).

LED strip watts per meter: reference figures

Watts per meter differs from strip to strip, so always use the figure on your own product page (Step 1 below). These are the figures we use in this guide and in our wiring diagrams:

Working in feet? 1 ft = 0.3048 m, so a 16.4 ft reel is 5 m. The calculator converts for you.

Addressable LED strips (WS2812B, SK6812, WS2811): power per pixel and per meter

Addressable strips use the same formula as any LED strip, but at 5 V the current is high. The figure in our wiring guide is 18 W/m for a 5 V WS2812B strip with 60 LEDs per meter, which is 0.3 W per pixel (18 W ÷ 60 LEDs).

• Long runs draw big current. 20 m of 5 V WS2812B at 18 W/m is 360 W, 72 A at 5 V. Two or three supplies are normal.
• Feed power every 5 m. Chain the reels for data (DOUT to DIN), but give every 5 m reel its own V+/GND pair from the supply. Do not pass power through the reels, and join all the GNDs, including the controller GND.
• Short 5 V strips too. A single 5 m, 5 V strip that goes red-brown at the far end needs power at both ends; use 18 AWG or heavier for the injection wires.
• Can’t inject every 5 m? With a 24 V addressable strip such as WS2815, one feed point covers 10–20 m.
• Controllers. With an SPI or WLED controller, the strip V+ comes from the supply, through the controller only if it is rated for the current.

SK6812, WS2811 and other ICs: the watts per meter differ from strip to strip, so take the W/m from the product page and put it in the calculator above with the strip voltage. More on wiring them: how to wire addressable LED strip lights.

Power supply sizing wiring diagrams

Drawn by the SuperLightingLED engineering team; wire colors follow our house convention (red V+, black V-/GND, green data). Click a diagram for the full notes in our LED strip wiring diagrams library.

Sizing the power supply. 5 m × 14.4 W/m = 72 W; add 20–30% headroom: 72 W × 1.25 = 90 W, so choose a 100 W supply. Never size the supply below the strip wattage.

12 V vs 24 V. At the same wattage a 24 V strip draws half the current. From one feed point: 12 V up to 5 m, 24 V up to 10 m. Strip, controller and supply must be the same voltage.

20 m single color run. One 24 V 300–350 W supply with four feed pairs, or two 150 W supplies each feeding two sections. Above about 300 W, use two supplies.

20 m addressable run. 5 V WS2812B at 60 LED/m is 18 W/m: 20 m is 360 W, 72 A at 5 V. Every 5 m reel gets its own V+/GND pair.

Many people do not know how to calculate the power based on the led strip, so there is no purpose when browsing the led power supply and don't know how to choose among the various power supply products.

An important principle for choosing an led power supply is whether the power is suitable for your LED strip lighting and led light controller. Actually, calculate the power that your LED light strip need is not a difficult thing.

There is a power calculation formula.

When calculating the power of your led strip light, you need to follow the 80% principle. The power wattage you choose is 1.2 times more than the calculated theoretical wattage. This way your power supply will not overheat and affect its service life.

4 steps to calculate the power you need

Take our 24V waterproof RGB color changing led neon lights as an example.

Step 1. Know the wattage per meter of your led strip.

The LED light strip product details page will detail the various information required for the product. Here you can see the specific number of watts per meter of your light strip.

After entering the product page, slide down the page to find the product specifications, which indicate the working power, and find the power per meter.

And we can know that this 24V RGB color changing led neon consumes 8 watts per meter.

Step 2. Decide how long you want the length of your light strip.

Led strip lights are generally 5 meters in a roll, but there are also cases of one meter or two meters in length. Even high-voltage strip lights can reach 100 meters.

Decide the length of your light strip reasonably according to your project. It can be unpleasant to find that there is a shortage of light strips when installing your led lighting.

Our 24V RGB neon lights have options of 5 meters, 10 meters, 15 meters and 20 meters. If you do not find the right length for you, you can contact us and we provide customized services.

Step 3. Calculate the theoretical power according to the power formula.

Multiply the wattage per meter by the length of the strip light to get the total theoretical wattage of the strip. 

Step 4. The 80% rule.

The actual required power is equal to the theoretical power multiplied by 1.2. That is, the power used by the strip light occupies 80% of the power supply.

Through calculation, we find that the 5m 24V RGB neon light actually needs a 48-watt power supply. And the longer the length, the more wattage required.

Not only our 24V RGB led neon rope lights, this calculation formula applies to any led strips. As long as you want to calculate the power of the power supply, you can use this formula.

Now, let's start to choose a suitable power supply for our 5m 24V led neon lights.

Find the led power supply drives in the categories. Click into the product category you are interested in, and find the power supply that matches the voltage and power. 

When choosing an LED power supply, it is required to know the characteristics of your light strip. For example, this led neon light is 24V, so we should choose 24V power supply. If you have waterproof requirements for the power supply, you should choose among the 24V waterproof power supply products. 

Among all 24V power supplies, there are 24V power adapters, 24V UL-Listed power supplies, and 24V waterproof power supplies. What is the difference?

►The 24V power adapter carrying power is relatively small.

►The 24V UL-Listed power supply has passed the UL certification, the quality is guaranteed, and has a five-year warranty. It provides IP20 non-waterproof and IP67 waterproof power supplies and Class II power adapters for you to choose.

►The 24V waterproof power supply has more waterproof function than the ordinary power supply, and it is more secure for outdoor use.

Therefore, a 5m 24V RGB led neon light with 48W should choose the 48W 24V power adapter, the 50W 24V UL-Listed IP20 power supply, the 50W 24V UL-Listed IP67 power supply, the 60W 24V UL-Listed Class II power adapter, or the 50W 24V waterproof power supply.

One thing to note is that when the power option does not have the same number as the actual required power you calculated, you need to choose a power that is a little larger than your number. 

For example, in the 24V UL-Listed IP20 power supply, there are no 48W power supply, it doesn’t matter to choose the 50W power supply.

If you need to install an led controller, the power required by the LED light controller is the same as the power required by the LED power supply, so the led neon light need a 48W LED controller.

*If you are looking for led controllers, you can read: How to choose led strip light controllers?

Conclusion

It is not difficult to calculate the power and choose the right power supply. Be patient and know more about it. You can do the job. If you have other questions, please feel free to contact us. 

*What you need to know about led light strip installation: 

How to cut led strip lights?

How to connect two light strips together?

How to wire single color led strip lights?

How to wire tunable white/CCT led strip lights?

How to wire RGB color changing led strip lights?

How to wire RGBW led strips?

How to wire RGBCCT led strip lights?

How to wire addressable led strips?

LED strip power calculator FAQ

How do I calculate the power for an LED strip?

Total wattage = watts per meter × length. Then follow the 80% rule so the strip uses no more than 80% of the power supply. Example: 8 W/m × 5 m = 40 W, and 40 W × 1.2 = 48 W, so the strip needs a 48 W supply or the next size up.

How many amps does my LED strip draw?

Divide the watts by the voltage. 60 W at 12 V is 5 A; the same 60 W at 24 V is 2.5 A. The controller and the wire must carry that current too.

How many watts per meter does a WS2812B LED strip use?

A 5 V WS2812B strip with 60 LEDs per meter is 18 W/m. 20 m is 360 W, 72 A at 5 V, so two or three supplies are normal and every 5 m reel gets its own power feed. For SK6812, WS2811 and other strips, use the W/m on the product page.

Should I choose a 12V or 24V LED strip?

At the same wattage a 24 V strip draws half the current, so it runs further: from one feed point, 12 V up to 5 m and 24 V up to 10 m. The strip, the controller and the power supply must all be the same voltage.

What if no power supply matches my number, and does the controller need sizing too?

Choose a power supply a little larger than your number: there is no 48 W 24V UL-Listed IP20 supply, so choose the 50 W one. If you install an LED controller, it needs the same power as the power supply, so the 48 W LED neon needs a 48 W LED controller.

LED strip power supplies

DC24V plastic shell power adapters24V power adapters for smaller loadsMeanWell UL indoor power supplies24V UL-Listed IP20 suppliesMeanWell UL outdoor power supplies24V UL-Listed IP67 suppliesDC24V MW Class II power adapters24V UL-Listed Class II adaptersDC24V waterproof power suppliesFor outdoor useDC12V MW UL-Listed power suppliesFor 12V LED stripsDC5V MW UL-Listed power suppliesFor 5V addressable strips such as WS2812BRGB LED neon lightsThe strip in our worked exampleAddressable LED strip lightsWS2812B, WS2815, SK6812 and moreWLED controllersOpen-source control for addressable strips