The amount of drying time needed for an interior primer depends on a few factors. These include the type of primer used, the type of surface it is applied to and the environmental conditions that exist at the time of application.
First is the type of interior primer used.
Acrylic and latex primers dry fast by design, typically 6-12 hours. While standard oil base primers can take a lot longer, 24 hours minimum and as long as 48 hours.
In order to speed up your interior painting project the fast drying stain blocking primers can be used. These interior primers dry to recoat in 1 hour in most cases.
Second is the type of surface the primer is applied to.
Porous surfaces, such as unpainted drywall or plaster, can be repainted sooner than slick sealed surfaces such as previously painted trim or metal. It takes the primer more time to form a good bond with slick surfaces.
Third is the environmental condition with in the room.
Higher humidity and cooler temperatures will slow down the drying process of all primers. Manufactures give drying and recoat times based on 74-76 degrees and 50% relative humidity.
The bottom line is 24 hours is usually enough time for most types of interior primers before top coating with your favorite paint. If the primer scrapes off easily with your fingernail or feels soft wait a few more hours before top coating.