A standard full bathroom is about 5 × 8 ft, or 40 sq ft. A 60 in tub fits across the 5 ft end, with the toilet and vanity on one long wall. The building code sets the minimum spacing: 15 in from the toilet’s centerline to anything beside it, and 21 in clear in front of the toilet and sink. The NKBA recommends roomier spacing: 18 in, and 30 in clear in front. Cedreo puts US bathrooms at 40 to 100 sq ft, with half baths as small as 20 to 30 sq ft.
Bathroom size planner
The planner lays out the classic small bathroom: a tub or shower base across one end, then the toilet and a vanity along one wall. It gives the room you need at code minimum or NKBA spacing.
The planner allows a toilet 30 in deep and 19 in wide, and a vanity top 22½ in deep. It checks the spacing beside the toilet and sink and the clear space in front of them. Our arithmetic.
Bathroom sizes by type
| Bathroom | What’s in it | Typical size |
|---|---|---|
| Full bath | Toilet, sink, tub (often with a shower) | 40–60 sq ft; 5 × 8 ft is the classic |
| Three-quarter bath | Toilet, sink, shower | about 40 sq ft (30–50) |
| Half bath (powder room) | Toilet, sink | about 18 sq ft (12–32) |
| Primary (master) bath | Often two sinks, a shower and a tub | 60–160 sq ft in newer homes |
Sizes from Cedreo’s bathroom size guide. See master bathroom dimensions for primary baths.
The 5 × 8 ft full bath comes from its fixtures: a standard tub is 60 in long (standard bathtub size), exactly the 5 ft end. Along the 8 ft wall, the tub’s 30 in, the toilet’s spacing and a 24 to 30 in vanity add up to 7 ft 3 in to 7 ft 6 in at code minimums.
The clearances that set the size
| Clearance | Code minimum | NKBA recommends |
|---|---|---|
| Toilet centerline to a fixture or wall | 15 in | 18 in |
| Sink centerline to a side wall | 15 in | 20 in |
| Two sinks, center to center | 30 in | 36 in |
| Clear in front of toilet, sink or tub | 21 in | 30 in |
| Clear in front of a shower entry | 24 in | 30 in |
| Shower, inside | 30 × 30 in, 900 sq in | 36 × 36 in |
| Separate toilet room | 30 × 60 in | 36 × 66 in |
| Door clear opening | local code | 32 in (a 2 ft 10 in door) |
NKBA Bathroom Planning Guidelines 1, 4, 5, 6, 9, 20 and 21, which quote the code minimums from the IRC (R307.1, P2705.1 and P2708.1). The code also requires a ceiling at least 80 in high over the shower area (IRC R305.1).
How to measure a bathroom
- Measure wall to wall both ways at floor level, past the baseboard, and multiply for the floor area: 5 × 8 ft is 40 sq ft.
- Measure the toilet’s rough-in, from the wall to the center of the drain bolts: usually 12 in (see toilet dimensions).
- Check the spacing from the toilet’s centerline to the tub, vanity or wall beside it: at least 15 in by code.
- Measure the clear floor in front of the toilet and sink: at least 21 in by code, 30 in for the NKBA’s comfort.
Questions people ask
What is the standard size of a bathroom?
About 5 × 8 ft (40 sq ft) for a full bath with a tub, toilet and sink. Cedreo gives 40 to 100 sq ft for US bathrooms in general.
What is the minimum size for a full bathroom?
With a 60 in tub across the end and a 24 in vanity, about 7 ft 3 in × 5 ft at the code’s minimum spacing, by our arithmetic; 8 ft 2 in × 5 ft at the NKBA’s.
How big is a three-quarter bathroom?
About 40 sq ft, from 30 to 50 (Cedreo): a shower in place of the tub. A 60 in shower base fits the same 5 ft end as a tub.
How much space do you need around a toilet?
15 in from its centerline to anything beside it and 21 in clear in front, by code; the NKBA recommends 18 and 30 in.
What is the smallest shower allowed?
30 × 30 in inside, and at least 900 sq in (IRC P2708.1). The NKBA recommends 36 × 36 in. See standard shower size.
Sources
- National Kitchen & Bath Association, Bathroom Planning Guidelines with Access Standards: Guidelines 1 (door), 3 (ceiling height), 4 (clear space), 5 and 6 (lavatory placement), 9 (shower size), 20 (toilet placement) and 21 (toilet compartment), with the IRC code requirements they quote
- Cedreo, The Average Bathroom Size: 40 to 100 sq ft in general; full, three-quarter and half bath sizes; primary baths 60 to 160 sq ft in newer homes
- Remodel Fit, toilet dimensions, standard bathtub size, standard shower size and standard cabinet depth: fixture and vanity sizes
Checked October 11, 2026. Metric values are converted. Room sizes in the planner and the text are our arithmetic from the clearances.