A 48x24-inch desk offers just enough surface for your 27-inch monitor and...

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

A 48x24-inch desk offers just enough surface for your 27-inch monitor and keyboard without feeling cramped. Keeping at least 36 inches of clearance behind your chair helps you move freely, making long gaming sessions more comfortable and less tiring