An LED strip stands or falls on the right measurements: how many metres, what power per metre, and a power supply that can keep up. Our free LED strip guide does the calculation for you – choose colour and brightness, enter the length, and get the right strip, a correctly sized power supply, a controller or dimming if needed, and a material list with part numbers and EAN.
How to plan an LED strip that lasts
An LED strip can deliver soft, hidden light under wall cabinets, along a staircase or behind a bed, but the result stands or falls on the planning. The most common mistakes are a power supply that is too small, a strip that is too long for the voltage, and a joint that can’t cope with moisture. The calculator above helps you with the sizing, and here you’ll get the reasoning behind the numbers, so you can make the right choices from the outset.
Size the power supply correctly
A strip draws a specific power per metre, stated in watts per metre. The maths is simple: multiply the consumption per metre by the number of metres, and add roughly 20 per cent on top as a buffer. If a strip draws 10 W per metre and you use five metres, the requirement is 50 watts, and with the buffer you should choose a power supply of at least 60 watts. The buffer ensures the supply isn’t running at maximum all the time, which means less heat and a longer service life. An undersized supply gets hot, hums and fails prematurely – it’s one of the most expensive savings you can make.
Length and voltage drop
An LED strip can’t be infinitely long on a single run. The longer the strip, the more the voltage drops towards the far end, and you see this as light that grows dimmer and often slightly more yellowish at the end. With low-voltage strips at 24V you can typically run further than at 12V before the drop becomes visible, because the higher voltage tolerates more resistance. If you need to cover long stretches, you can feed the strip from both ends or run separate supply cables to each section. 230V strips can be laid in very long lengths without noticeable voltage drop, but they are cut at coarser intervals and require a different setup than low voltage.
Choose the right IP rating
The IP rating tells you how well the strip withstands dust and water. For dry rooms such as the living room, bedroom and under the kitchen’s wall cabinets, an open IP20 strip is fine and the cheapest option. If the strip is going somewhere with moisture, splashes or outdoors, it needs protection. IP65 withstands splashing water and is well suited to the bathroom and the back edge of the kitchen worktop, while IP67 withstands heavy water exposure and brief immersion, making it right for eaves, terraces and other exposed positions. Always choose the IP rating according to the wettest place the strip will come near – including at joints and ends, which must be sealed properly.
Three ways to dim
There are several ways to dim an LED strip, and the choice depends on your installation. The most flexible option on low voltage is a controller between the power supply and the strip, which often also controls colour and can be operated by remote or app. Alternatively, you can use a dimmable power supply, where the supply itself regulates the power. On 230V strips you instead control it with an ordinary wall dimmer, provided both strip and dimmer are designed for one another. Whichever method you use, the strip, supply and dimmer must work together – don’t mix components that aren’t specified to work together if you want to avoid flicker.
An aluminium profile is more than decoration
An aluminium profile solves three things at once. First, aluminium draws heat away from the diodes, and cooler operation means a longer service life and a more stable light colour. Second, a profile with a frosted cover hides the individual points of light, so you see an even line rather than a row of dots. Third, the profile gives a clean, easy-to-mount edge that protects the strip and makes the installation neater. Especially in visible positions and with SMD strips, the profile is what lifts the result from home-made to professional.
Colour temperature and colour rendering
Just as with spotlights, you choose the colour temperature to suit the room. 2700K is warm and cosy for the living room and bedroom, 3000K is slightly more neutral, and 4000K is cool and functional for the wardrobe, workshop and work zones. Also look at the colour rendering: a strip with CRI90 to 95+ renders colours true to life, which matters in particular under wall cabinets, where you handle food, and anywhere textiles and materials need to look right. Low CRI makes those same colours flat and dull.
COB or SMD?
Traditional SMD strips have visible, separate diodes that you can count up close, and they can give a dotted light without a good profile. COB strips have the diodes covered by a continuous layer, so the light appears as a single unbroken line with no dots at all. HiluX COB strips therefore give a markedly more even result, especially in profiles and in places where the strip is seen directly. For ambient lighting, shelves and cornices, COB is usually the neatest choice.
Cut, join and mount correctly
An LED strip may only be cut at the marked cutting points, where you’ll typically see a pair of scissors or a line with copper pads. If you cut anywhere else, you’ll ruin a segment. For joints you use either soldered connections or quality click connectors, and in wet positions both the joint and the end must be sealed so that water can’t get in. Clean and dry the mounting surface thoroughly before you press the self-adhesive backing into place, and lay the strip in a profile wherever possible. Careful mounting is the difference between light that lasts for many years and light that falls down or fails after a single season.
Frequently asked questions about LED strips
How large a power supply should I choose?
Multiply the strip’s consumption in watts per metre by the number of metres, and add roughly 20 per cent as a buffer. If you use five metres at 10 W per metre, the requirement is 50 watts, so you choose at least 60 watts. The buffer keeps the supply cooler and extends its service life.
Why does the end of my strip get dimmer?
This is caused by voltage drop over the length of the strip. The longer the run, the more voltage is lost towards the far end. The solution is to feed the strip from both ends, split it into shorter sections each with its own supply, or choose 24V rather than 12V, which tolerates longer runs.
Which IP rating should I use in the bathroom?
For damp positions such as the bathroom, at least IP65 is recommended, which withstands splashing water. If the strip is exposed to heavy water or sits outdoors, choose IP67. Remember to seal both the joints and the ends so that water can’t get inside the strip.
Can I dim an LED strip?
Yes, in three ways. On low voltage you use a controller between the supply and the strip, or a dimmable power supply. On 230V strips you use an ordinary wall dimmer. The important thing is that the strip, supply and dimmer are specified to work together, otherwise you risk flicker.
Is an aluminium profile necessary?
Not always, but it’s recommended in all visible positions. The profile draws heat away and extends the service life, hides the individual points of light so you get an even line, and protects the strip. In hidden, dry positions you can do without it, but the result is neater with one.
What’s the difference between COB and SMD?
SMD strips have visible, separate diodes that can give a dotted light. COB strips have the diodes covered by a continuous layer, so the light becomes a single unbroken line with no dots. COB gives the most even result, especially where the strip is seen directly, and is usually the neatest choice for ambient lighting.