A 4 BHK builder floor is usually the whole of one level on a South Delhi plot: four bedrooms, a formal living and dining area, and a kitchen. Because it occupies an entire floor rather than a slice of a tower, the layout — not the carpet area alone — decides how well it actually lives.
What to examine at this size
Bedroom-to-bathroom ratio. Four bedrooms served by two bathrooms is a daily friction point on a single floor. Three is the practical minimum for a family of five or more.
Servant quarter provision. On four-bedroom floors this is usually expected, but whether it is a genuine room with a window or a converted store matters for both comfort and resale.
Lift. A 4 BHK on an upper floor without a lift is a hard resale, regardless of how good the floor itself is.
Parking for two cars, since a four-bedroom household usually runs two. On tighter plots the stilt is the constraint.
Terrace rights, if you are considering the top floor. Establish in writing whether the roof is exclusive to you or shared.