Bathroom
Bathroom dimensions
The bathroom is the room where the legal minimum and the comfortable dimension are furthest apart, and knowing both is the whole job.
Short answer
Code lets a toilet sit 15 in (38 cm) from its centreline to a wall with 21 in (53 cm) of clear floor in front. The NKBA recommends 18 in (46 cm) and 30 in (76 cm). Both numbers are correct, and knowing which one you are working to is the difference between a legal bathroom and a pleasant one.
The numbers, at a glance
- Toilet centre to wall, code
- 15 in (38 cm)IRC P2705.1
- Toilet centre to wall, recommended
- 18 in (46 cm)NKBA
- Clear floor in front of a fixture
- 21 in code, 30 in recommended
- Minimum shower interior
- 30 x 30 in (76 x 76 cm)IRC; 36 x 36 in in practice
- Vanity height
- 32 to 36 in (81 to 91 cm)
- Vanity lighting at the face
- About 1,600 lm at CRI 90+
Two documents govern a bathroom and they do not agree, on purpose. The International Residential Code sets the minimum a building official will pass. The NKBA planning guidelines set what a designer would specify if the room allowed it. The gap between them is typically 3 to 9 in (8 to 23 cm) per fixture, and in a small bathroom that gap is the entire design problem.
This section always gives both, labelled. A page that quotes only the comfortable number is useless when you are fitting a shower room under a stair; a page that quotes only the code minimum will talk you into a bathroom you dislike for a decade.
| Dimension | IRC minimum | NKBA recommendation |
|---|---|---|
| Toilet centreline to any wall or fixture | 15 in (38 cm) | 18 in (46 cm) |
| Clear floor in front of toilet | 21 in (53 cm) | 30 in (76 cm) |
| Clear floor in front of lavatory | 21 in (53 cm) | 30 in (76 cm) |
| Lavatory centreline to side wall | 15 in (38 cm) | 20 in (51 cm) |
| Shower interior | 30 x 30 in (76 x 76 cm) | 36 x 36 in (91 x 91 cm) |
| Ceiling above fixtures | 80 in (203 cm) | 80 in (203 cm) |
What that buys you in floor area#
A toilet in a 30 in (76 cm) wide alcove is legal. In a 36 in (91 cm) alcove, your elbows clear the wall and the roll holder is reachable without leaning. The 6 in difference is roughly 5% of the floor of a typical 5 x 8 ft (1.5 x 2.4 m) bathroom, which is almost always available somewhere else in the plan: a 18 in (46 cm) deep vanity instead of 21 in, a wall-hung toilet with an in-wall cistern, or an outswing door.
In this section#
- Bathroom fixture clearancesBathroom clearances: toilet centreline 15 in (38 cm) minimum by IRC, 18 in recommended by NKBA, 21 in clear in front by code, 30 in to be comfortable.
- Bathroom mirror and lighting heightsMirror height and width over a vanity, sconce positions that cross-light the face, and the lumen and CRI targets that matter.
- Shower sizes and clearancesShower sizes: 900 sq in (0.58 m2) and a 30 in circle is the IRC minimum, 36 x 36 in (91 x 91 cm) is the real minimum, 36 x 48 in is comfortable.
- Small bathroom layouts that workWorked small bathroom plans with real dimensions: 3 x 6 ft shower room, 5 x 7 ft full bath, 6 x 8 ft, plus the six moves that buy inches.
- Vanity heights and sizesBathroom vanity heights: 32 to 34 in (81 to 86 cm) traditional, 36 in (91 cm) comfort height, plus widths, depths and the elbow arithmetic that decides.