Screen size and desk depth

From desk depth to viewing distance

Three lengths add up between your eyes and the panel: the position of your head relative to the front edge of the desk, the depth of the desk itself, and the space the monitor leaves behind it.

Seated at a keyboard, forearms resting on the desk, the eyes of an adult are about 10 cm in front of the edge, on the chair side. At the other end, a monitor on its stand does not touch the wall: the foot is 18 to 25 cm deep and the panel hangs in front of the column, about 15 cm from the rear edge of the desk. On an arm clamped to the rear edge, the panel can be pushed back to about 5 cm from it.

distance ≈ desk depth + 10 − 15 = depth − 5 cm (on a stand)
distance ≈ desk depth + 10 − 5 = depth + 5 cm (on an arm)

These are averages. A deep stand, a wall-mounted screen, a keyboard tray or a habit of leaning back shift the result by a few centimetres; measure if you can. But the order of magnitude is robust, and it is what the selector uses when you give a desk depth without a measured distance.

What each desk depth allows

The previous chapter established that a 16:9 screen is comfortable between 0.9 and 1.2 diagonals. Combined with the estimate above, each desk depth has its natural size.

60 cm: the territory of 24 inches

The commonest depth for home desks puts a monitor on its stand 55 cm from the eyes. A 24-inch screen fills 51 degrees there, at the top of the comfortable band. A 27-inch fills 57 degrees: usable, but the corners require head movement, and its 34 cm of height brings the top edge close to eye level on a fixed stand. With an arm the distance rises to 65 cm and 27 inches becomes the right size.

70 to 75 cm: 27 inches

At 65 to 70 cm a 27-inch screen fills 46 to 49 degrees, the middle of the band. This is the combination most office desks and most 27-inch monitors are designed for, which explains the success of the format.

80 cm: 27 or 32 inches

At 75 cm, a 27-inch screen (43 degrees) and a 32-inch screen (50 degrees) both fit. The choice is a matter of use: 32 inches gives larger content at the same resolution, or more room with 4K, and suits those who want to sit back from the screen. A 34-inch ultrawide (56 degrees) is also in its band.

90 cm and more: 32 inches and wide formats

From 85 cm a 27-inch screen starts to look small (39 degrees), and its pixels are already finer than the eye can separate: the distance would serve a larger screen better. A 32-inch screen is at its best, and wide formats of 34 to 40 inches find the distance they need. Very large 16:9 screens, 40 to 43 inches, need more still: over 1 m, or a wall mount behind the desk.

Real dimensions: what a diagonal hides

A diagonal is a convenient label and a poor description. The surface depends on the aspect ratio:

16:9 screen: width = 0.872 × diagonal, height = 0.490 × diagonal
21:9 screen: width = 0.922 × diagonal, height = 0.386 × diagonal

Three consequences are worth keeping in mind.

Going from 24 to 27 inches adds 7 cm of width and 4 cm of height: 28% more surface. From 27 to 32 inches the gain is 10 cm and 5.5 cm, 36% more surface. Each step is clearly visible.

A 34-inch ultrawide is a 27-inch screen made wider. Its height, 33 cm, is that of a 27-inch 16:9 screen; it adds 20 cm of width. A 29-inch ultrawide has the height of a 23-inch screen, which surprises many buyers.

Width also has to fit. A 34-inch screen measures 82 cm with its bezels, a 49-inch 120 cm. On a 120 cm desk the first leaves room for speakers and a lamp; the second leaves none.

The comparison of formats gives the width, height, density and comfortable distances of every size sold in volume.

Gaining distance on a shallow desk

When the desk is too shallow for the screen you want, four measures help, in decreasing order of effect.

• A monitor arm. Clamped to the rear edge, it gains about 10 cm and frees the surface under the screen. Check that the monitor has VESA mounting holes (100 × 100 mm on almost all models up to 32 inches) and that the arm carries its weight: 4 to 7 kg for a 27-inch, up to 10 kg for a curved 34-inch.
• A wall mount, when the desk stands against a wall: the panel sits at the very back, 3 to 5 cm beyond what an arm allows.
• A compact stand. Some monitors have a flat rectangular foot only 18 cm deep, others a V-shaped foot of 28 cm. On 60 cm the difference matters.
• Pulling the desk away from the wall by 10 cm lets the foot overhang at the back; inelegant, effective.

Leaning back in the chair is not a solution: the keyboard and mouse stay where they are, and the arms end up stretched.

What does not help is choosing a curved screen to “bring the edges closer”. Curvature reduces the angle at which you see the sides of a wide screen; it does not reduce the viewing angle the screen occupies. A 34-inch curved screen at 55 cm is still too wide.