Desk size calculator

Quick answer

Two 27 in 16:9 monitors are 47.7 in of screen once you allow for the gap between them, so a dual 27 in setup needs a desk about 63 in wide. Depth matters more than people expect: a factory stand eats about 9 in of it, while a clamp arm needs about 3 in and gives the rest back.

Screen width is exact trigonometry from the aspect ratio. The margins, the keyboard zone and the depth taken by each mounting method are conventions drawn from published product dimensions.

Desk width needed -
Desk depth needed -
Screens alone -
Viewing distance -

Width = screens x screen width + gaps + 8 in margin each side. Screen width = diagonal x 0.872 for 16:9. Depth = viewing distance - 4 in eye setback + mounting depth - keyboard zone, floored at mounting depth + 11 in.

Desks at the sizes this works out to

Shown across the range this category actually spans, from $99.98 to $719.99, rather than the cheapest few.