A primary bathroom layout fails differently from a small one. There is enough space, so nothing is impossible — the mistake is spreading fixtures evenly across the room and ending up with a bathroom that is large but not comfortable. A good master bathroom layout starts from what each feature actually needs.
The honest trade at 100 to 120 square feet is the tub. A large, well-detailed shower usually beats a cramped shower plus a tub nobody uses — most master bathroom layout regrets start with trying to keep both in a room that will not take them.
This is the organizing idea behind almost every primary bathroom layout that works. Put the wet functions together — shower, tub, and the waterproofing and drainage they need — and keep the dry side for the vanity, storage and dressing.
It pays off three ways: plumbing runs stay short and cheap, the waterproofed area stays compact, and two people can use the room at once without crossing paths. It also makes a wet room possible later, where the tub sits inside the shower enclosure behind one glass panel.
Same room, same 120 square feet, four genuinely different plans. Which one suits you depends less on taste than on how two people use the room at once.
One more variation worth knowing: a split vanity, with the two basins on opposite walls rather than side by side. It removes the morning bottleneck entirely and is the quiet favourite among couples who have lived with both.
Most double vanities are ordered by cabinet width and then disappoint. The spacing is what matters:
If the wall will not take 84 inches, that is the room telling you it is a single-vanity bathroom. A cramped double is worse than a good single.
An enclosed toilet is the feature people rank highest after a double vanity, and the one most often drawn too small.
Keeping at least one tub in the house matters for resale — that argument, and where it does not apply, is in our pre-sale guide.
Everything above assumes you can put fixtures where the layout wants them. Relocating a toilet, sink or shower means moving drain and vent lines, and taking out a wall may be structural — all permitted work in every Bay Area city, with plans and inspections.
That is worth knowing before the design stage, not after. The clearance minimums every plan has to satisfy are in our small bathroom layout guide, and the finish decisions that follow are covered in bathroom remodel ideas.
About 100 square feet is where a primary bathroom starts to feel like one — enough for a double vanity and a generous shower, or a single vanity with a shower and a tub. Around 120 square feet, commonly a 10 by 12, is where a double vanity, a separate shower and a soaking tub all fit comfortably at once, which is why it is the usual target. At 140 square feet and above you can add an enclosed water closet, a genuinely large shower, or a wet room. Below 100 square feet, prioritise: a large shower and a good single vanity beats a cramped version of everything.
The NKBA recommends at least 36 inches between the centerlines of the two sinks. That gap is not decorative — it decides elbow room, usable counter between the basins, and whether two people can stand at the vanity without negotiating the same space. You also want about 20 inches from each sink centerline to the nearest wall or tall cabinet, against a code minimum of 15. In practice you need roughly 84 inches of wall to carry a 72-inch double vanity with proper clearance on both sides.
A 10 by 12 gives you 120 square feet, which is the size where a double vanity, a separate shower and a soaking tub all become realistic together. The layout that works best zones the room: shower and tub grouped on one wet side, vanity and toilet on the dry side. That keeps plumbing runs short, limits the waterproofed area, and lets two people use the room without crossing paths. Adding an enclosed water closet on top of all three is usually a stretch at this size — that generally wants 140 square feet or more.
Thirty by 60 inches is the practical minimum for an enclosed water closet, and 36 by 66 inches is where it stops feeling like a cupboard. Fitting one alongside a shower and vanity generally means a bathroom of roughly 55 to 60 square feet or more. Use a pocket door rather than a swing door — a swing door consumes the very clearance the compartment needs, and it is a cheap change at the plan stage that is expensive to add later.
Traditional vanities run 32 to 34 inches high. Comfort height, at 34 to 36 inches, has become the more common choice for primary bathrooms because most adults find the posture better and it makes mirror and lighting alignment easier to get right. The main reason to stay lower is a bathroom used by young children. It is worth deciding early, because the height affects mirror placement, sconce heights and backsplash detailing.
In a room under about 120 square feet, one done well beats two done badly — a large shower with a bench usually delivers more daily value than a cramped shower plus a tub that goes unused. Above that size you can have both comfortably. The resale caution is separate from the comfort question: keeping at least one bathtub somewhere in the house protects your buyer pool, particularly with families, so converting the primary bath is safest when another tub exists elsewhere.
Grouping the shower and tub together as a wet zone, and keeping the vanity, storage and dressing area as a dry zone. It is the organising principle behind most primary bathrooms that work well. The practical benefits are that plumbing runs stay short and cheaper, the waterproofed area of the room stays compact, and two people can use the bathroom at the same time without crossing each other's path. It also leaves the door open to a wet room later, where the tub sits inside the shower enclosure behind a single glass panel.
