A 48x24-inch desk gives you enough space for your keyboard, mouse, and a...

https://annamaid.com/is-osha-a-good-reference-for-home-desk-ergonomics/

A 48x24-inch desk gives you enough space for your keyboard, mouse, and a 27-inch monitor without feeling cramped. Pair that with at least 36 inches of clearance behind your chair to move comfortably during those long gaming sessions