A 48x24-inch desk gives you enough space for a 27-inch monitor and room to move...

https://scarlettsnewnews.nexorafield.com/posts/how-do-i-plan-a-setup-so-i-can-still-open-drawers-and-cabinets

A 48x24-inch desk gives you enough space for a 27-inch monitor and room to move your mouse comfortably. Leaving about 36 inches of clearance behind your chair ensures easy movement without feeling cramped