A 48x24-inch desk gives you enough room for a 27-inch monitor and your keyboard...

https://inchesguide.com/how-much-space-do-you-need-for-a-comfortable-home-gaming-setup-a-measurement-guide/

A 48x24-inch desk gives you enough room for a 27-inch monitor and your keyboard without feeling cramped. Pair that with at least 36 inches of clearance behind your chair to move freely