It always depends on the proportions of the room, the location of windows and doors, etc. A room of 2x6 m will hardly be usable with an L-shaped kitchen and a table for 4 people, while 3x4 m is more likely ... but both are 12 sqm. However, a functional kitchen can also be realized in 2x6 m.
And, in a 3x4 m room with doors in the middle on both 4 m sides will again be less usable than a 3x4 m room that has only one door on one of the 3 m sides.
And then there are very individual requirements for the kitchen, kitchen equipment, work surface, etc.
Understood? Square meter numbers say little to nothing in this context.