Constitution class decks
The decks of  Federation starship:

Original configuration 

 Deck 1
 Bridge (, et al.)

 Deck 2
 Guest quarters ()

 Deck 3
 Engineering (Impulse Deck)  ()
 Recreation room 3 ()
 Recreation room 6 ()
 Crewmen's lounge ()

 Deck 4
 The forward edge of the ship ()
 Crew quarters ()
 Environmental control ()
 Auxiliary communications juncture ()

 Deck 5
 Sickbay ()
 Engineering (Impulse Deck) ()
 Engineering computer room ()
 Transporter room ()
 Recreation room ()
 Recreation room 3 ()
 Captain's quarters ()

 Deck 6
 Briefing room ()
 Crew quarters ()
 Guest quarters ()
 Main life support couplings ()

 Deck 8 (H deck) 
Auxiliary control ()
Evaluation laboratory ()
Weapons locker ()

 Deck 9
Section 2
Crew quarters
3F 125: Spock ()
3F 127: Leonard McCoy ()
Life sciences department: Botany section ()
Atmospheric system ()
Section 4
 Briefing room ()

 Deck 11
 Section A3
 Engineering circuit bay ()

 Deck 12
 Crew quarters 
 3C 46: Janice Rand () 
 3F 121: James T. Kirk ()

 Deck 14
 Transporter room ()
 Engineering support ()
 Section C
 Personnel director's office ()

 Deck 21 
 The habitable aft-end of the ship ()
 Power relay ()

 Deck 22
 Power transfer conduits ()

 Bottom deck:
 Hatch to satellite bay (, remastered)   
 Hatch to decontamination tanks spray release (, remastered)

Refit configuration 

 Deck 1
 Bridge (, et al.)

 Deck 3
 (C Deck) Science officers quarters ()

 Deck 4
 (D Deck) Admiral's quarters (,  Kirk is shown leaving the turbolift on D Deck before talking to Dr. Marcus in his quarters.)

 Deck 5
 Officers' quarters ()
 (Level 5) Captain's quarters ()

Deck 13 
 Torpedo bay ()

Background information 
The following deck layouts come exclusively from the , by Michael Okuda and Denise Okuda. 
 

 
The following deck layouts come from The Making of Star Trek, by Stephen Whitfield for the original configuration primary hull and from Mr. Scott's Guide to the Enterprise, by Shane Johnson for the refit configuration.

There is a discrepancy in The Making of Star Trek with the description of the primary hull as being eleven decks in height, but shown to be nine decks in height in a cutaway diagram. The secondary hull is stated to be sixteen decks in height, but shown in the diagram to be eight decks, with no exact locations given for the following features: fuel storage, supplies storage, main repair centers, water and waste reconversion, minimal quarters for engineers and star-drive personnel used only in the case of saucer separation and the hangar deck.

The most recent canonical cutaway graphic of the original Constitution-class was featured in . The graphic was originally produced by Doug Drexler for the Star Trek: Captain's Chair CD-ROM.  It was also featured in the The official STAR TREK prop and costume auction catalog, pp. 36-37.  In this image several key locations of the interior of the ship are recognizable as depictions, some are marked and labeled. The schematic depicts the ship as having 27 decks, and one more above deck 1 in the nacelles. The marked areas in this layout are: