When buying LED strip there are several parameters you should be looking at. One of those is how many LED modules have been placed per meter of strip. Price is very often directly tied to this parameter because the higher the density of LED modules on a strip the more the cost of the strip will be!

Common values are given in either LEDs/m or total amount of LEDs per 5 meter (length most strip gets sold in). Take a look at this following illustration and the table below it to see the difference it makes for the total numbers.
 

More LEDs, more better?

Generally speaking you can say that using more LEDs per meter is always better but read the following points:

Some of the Pro’s are:

• Generally a higher light/lumen output
  • Though this is certainly not always the case because it depends on the LEDs used, a 60LED/m strip can be brighter than a 120LED/m strip!
• Better shadow forming because a higher density of LEDs/m fuse together to look like one source quicker
• Better LED light and color uniformity again because of fusing together much quicker
• More LEDs/m provide a more fluent animation on Digital LED strip

Some of the Cons are:

• Generally worse voltage drop the higher the LEDs/m becomes
  • 5v 144LEDs/m strip often doesn’t come longer than 1m because of this
  • 144 LEDs/m strip is often 12mm wide instead of 10mm wide
• Worse heat spreading
  • Because all the LEDs are closer together more heat is concentrated together
• Higher count LEDs/m strip quickly become more expensive
  • Packing those LEDs together asks for higher quality strip to mount the LEDs on and sellers ask a premium for it

How much LEDs/m do you need?

You need to figure out per project how many LEDs/m you are going to need. If the LEDs are close to a diffuser for instance you want as much LEDs/m you can get so that you can’t see the individual LEDs anymore. But if you are lighting an object that isn’t 1cm away but for instance 30cm away, lower amount LEDs/m strip will be fine and blend together way before it reaches your object.

Nowadays I mostly pick up 96LEDs/m or 120LEDs/m strip both in white or color versions since prices for those versions have come down over the last year or so. For Digital LED strip I go with either 60LEDs/m or 144LEDs/m depending on how far away the viewing subject will be. A 144LEDs/m strip will make animations look more fluenent because there are more “steps”.

Length – LEDs/m – Cost balance

For my personal projects I mostly look at the balance between LEDs/m and cost while also taking length into account. But with a lot of strips now coming with 120LEDs/m and still being relatively affordable, using 24v and double feeding, a high quality 120LEDs/m strip can still be used up to 5m without a problem! At full brightness one of these strips might use up to 140 watt though, so make sure you know what you want to use them for and use the right thickness of wire and power supply! The same strip but with 60 LEDs/m would only use up to 70 watt max! So try to find a balance between what you need, want and what it costs.