Of everything on a desk, the mat is the thing people most often get wrong by a couple of centimetres. It is also the one item where a couple of centimetres decides whether it looks deliberate or looks like a mistake.
Measure the usable width, not the desk
The number you want is not the width of the desk. It is the width you can actually cover: desk width minus anything fixed at either end — a monitor arm clamp, a shelf leg, a cable tray bracket. Clamps typically eat 4-6 cm on the side they sit on.
Measure the depth you will actually use
Most desks are 60-80 cm deep, and most of that depth behind the monitor is dead space. Measure from the front edge to where the monitor stand begins. That is your working depth, and a mat deeper than it will disappear under the stand.
Then subtract a breathing margin
Take 2-3 cm off each side of your usable width. A mat that lands exactly flush against a clamp or a wall will bow in the middle within a week, and a bowed mat never lies flat again.
Common sizes, and what they suit
- Around 80 x 30 cm — keyboard and mouse only, on a shallow desk or a desk you share with paperwork.
- Around 90 x 40 cm — the common "full desk" size. Covers a keyboard, a mouse with room to move, and a notebook beside them.
- Larger than that — worth it on a 140 cm-plus desk, where a smaller mat reads as a placemat rather than a surface.
Thickness changes how it feels, not how it looks
A 2 mm mat is a surface. A 4 mm mat is a cushion, and it lifts your keyboard by a noticeable amount, which changes your wrist angle. If you already use a wrist rest, go thinner; if you do not, thicker is kinder.
Every mat in Mats & Wrist Rests lists its sizes and thickness in both inches and centimetres. If you are between two, send us the measurement at contact@cozyn.store and we will tell you which one we would pick.