Which monitor light to buy: size guide by screen inches

Sunrise IT · 14 August 2026

If you have made it this far, you have probably seen an LED bar on someone's desk and are wondering which one is right for you. The question is almost always the same: what length to buy and whether it is worth paying more for RGB. Let's take it step by step.

The size rule: a little less than your screen

An LED bar should cover roughly the width of the monitor's picture area, or slightly less. If it is too short, the light only falls on the centre of the desk and the sides stay dim. If it is too long, it sticks out past the edges and looks odd.

As a practical guide:

21 to 24 inch monitors: a 30 cm bar is enough.
24 to 27 inch monitors: 40 cm is ideal.
27 inch and larger, and ultrawide monitors: 44 cm or more.

If you are torn between two sizes, always go for the smaller one. A slightly short bar lights well; one that is too long throws the whole look off balance.

Why it does not reflect on the screen

This is the most common question, and the answer lies in the direction of the beam. A ceiling light or a desk lamp emits light in every direction, and some of it bounces off the monitor glass right where you are looking. An LED bar is mounted on the top edge of the screen and aims the light down and forwards, onto the keyboard and desk. The monitor stays behind the beam, not inside it.

The real problem is not the screen, it is the contrast

Many people think eye strain when working at night comes from the brightness of the monitor. It actually comes from the jump between a very bright screen and a dark room. Your eyes spend hours adjusting between those two levels. Lighting the desk reduces that contrast and makes long sessions much easier.

That is why colour temperature matters: warm light suits the evening better, and neutral or cool light works better during the day or when you need to concentrate.

White light or RGB?

A white-light model does one thing: it lights the desk with different shades of white. That is what you need if you study, work from home or read.

An RGB model adds a second light strip pointing backwards, at the wall, and paints the area behind the monitor with colour. It does not light the desk: it is purely ambience. It makes sense if you have a gaming setup or like the backlight effect in videos and photos.

The key is that on good models the two lights are controlled separately, so you can use only the white one while you work and switch the colour on when you play.

Details worth checking before you buy

5V USB power: saves you a wall socket. It plugs into the monitor itself, the laptop or any charger. Important: do not use higher-voltage adapters.
Mounting system: an adjustable counterweight is the most convenient, because it simply rests in place with no screws.
Memory function: it remembers the last setting when you switch it on. It seems trivial until you have to set it up again every morning.
Colour rendering index (CRI): above 90, colours look true to life. It matters if you draw, edit photos or check printed documents.
Stepless brightness control: better than one that jumps between three or four fixed levels.

Summary

Choose the length according to your monitor's inches, decide whether you only need work light or colour ambience as well, and check that it is USB powered and has a memory function. With that you have got 90% of the decision right.