The two dimensions that decide a small bathroom
Ask someone why their bathroom feels cramped and they will say it is too small. Measure it and the floor area is usually adequate for what is in it. What is not adequate is one of two things: the space in front of the toilet, or the arc of the door.
Front clearance at the toilet is the harder one because the toilet is the fixture that cannot move. It sits over a waste connection in the floor, and relocating that connection means opening the floor, reworking the drain and the vent, and getting it inspected. Everything else in the room can slide along a wall for the cost of some tile. So a layout that puts the vanity or the tub too close to the front of the toilet is a layout that has to change, not a plumbing job waiting to happen.
The door is the second, and it is the one people discover on the day it is hung. A 28 inch leaf sweeps a quarter circle of about four and a quarter square feet, and in a room the size of a hallway that arc lands on something. A door that stops at fifty degrees still lets you into the room, but sideways, and it will annoy you daily for as long as you own the house.
How the clearances are measured here
| What it reports | How it is measured | What it does not include |
|---|---|---|
| Space in front | Straight out from the fixture centreline to the opposite wall, or to the first fixture standing in that line | Something that blocks part of the fixture width but misses its centreline |
| Space beside | From the fixture centreline outward to the nearest neighbour edge or the corner | Trim, a shower curb, a vanity door that projects when open |
| Door stop angle | The first angle at which the swinging leaf touches any fixture rectangle | Anything not entered as a fixture — a bin, a towel hook, a radiator |
Fixtures are treated as rectangles against a wall, which is how they behave for clearance purposes even when the porcelain is curved. A toilet is roughly 20 inches wide by 28 to 30 deep, a vanity is its cabinet size, and a tub is usually 30 to 32 by 60. Use the actual dimensions from the specification sheet for anything already chosen.
The numbers are yours, and here is why
This page will not tell you how much room a toilet needs. Clearances at plumbing fixtures, the width in front of a water closet, the space each side of its centreline, exhaust ventilation, receptacle locations and which of them need ground fault protection are all set by the code your jurisdiction has adopted, and jurisdictions adopt different editions with different amendments. The local building department is the authority on what applies to your address, and they answer this question routinely.
Accessibility is a further layer with its own and generally larger figures, and whether it applies depends on the building and the work. If someone in the household uses a walker or a wheelchair, or might, the clearances to design for are not the minimum ones and the question is worth putting to someone who specialises in it before the walls go up.
What the calculator does is compare a layout against whatever targets you enter, which is the part a code official cannot do for you over the phone. Put the required figures in the fields once you have them, and the comparison becomes meaningful.
When the door is the problem
There are four fixes and they are not equal. Rehanging on the opposite jamb is nearly free and often solves it completely, since the arc simply moves to the other side of the opening. Reversing it to swing out costs almost nothing in the bathroom and moves the problem to the hall, which is fine unless the hall is narrow or the door lands in a traffic path. A pocket door removes the arc entirely, but it needs a stud bay with nothing in it, and in a bathroom that rules out any wall carrying supply pipe, waste, or a vent stack, which is frequently most of them. A barn door slides on the face of the wall, needs clear wall to slide onto, and does not seal or latch the way a hinged door does.
Work out which you have before demolition rather than after, because the framing for a pocket door happens at the same time as everything else behind the wall. The door swing planner handles the swing in more detail along a single wall, and the pocket and barn door calculator covers what the sliding options need. Rough opening sizes for whichever you choose come from the rough opening calculator.
After the layout
A settled bathroom layout is the start of the material list, not the end of the planning. Waterproofing and substrate under the tile come first, sized with the backer board calculator, and the tile layout above it decides where the cut course lands, which the tile layout calculator works out. Hot water demand for a bathroom being added rather than replaced is a question for the water heater sizing calculator, and the fixture load on the supply side belongs with the fixture unit calculator. None of those matter until the fixtures have somewhere to sit.
Questions people ask
How much space is needed in front of a toilet?
That is set by the code your jurisdiction has adopted, not by a general rule, and it differs between editions and between local amendments. It is also the single most common reason a small bathroom layout has to change, so it is worth getting the actual number from the building department before you draw anything rather than after. Put whichever figure applies to you into the front target field on the toilet line and the comparison against your room becomes meaningful. Where accessibility requirements apply the figures are different again and generally larger.
Can I move a toilet a few inches?
Physically yes, practically it depends entirely on what is under the floor. The toilet sits on a flange connected to a waste line that has to fall toward the stack at a consistent slope and has to be vented. Moving it along the direction of the run is sometimes straightforward and moving it across the joists frequently is not, because the drain cannot pass through a joist wherever it likes. On a slab it means breaking concrete. In every case it is licensed plumbing work under a permit in most jurisdictions and it is inspected. Find out what is possible before designing a layout that depends on the toilet moving, because the answer occasionally is that it cannot.
Should a bathroom door swing in or out?
In is the convention because an out-swinging door in a hallway is a hazard to anyone walking past and can conflict with other doors. In a small bathroom the in-swing is also what eats the layout, which is the whole tension. Before reversing it, check the hall: whether there is clear wall for the leaf to sit against, whether it will strike another door, and whether it blocks a route. There is also a safety argument for out-swing that is worth knowing, which is that a door swinging out can be opened if someone has collapsed against it inside. Whether either direction is permitted where you are is a question for the building department.
What size bathroom do I need for a tub, toilet and vanity?
There is no single answer because it depends on the required clearances where you live and on the fixtures you choose. What the arithmetic can tell you is the shape of the problem. A tub is typically 60 inches long and 30 to 32 deep, so it fixes one wall almost entirely. A toilet needs its own width plus side space plus front space, and a vanity needs front space to stand at. Line those up along the walls in this calculator with your own targets and the room either closes or it does not. Where it does not, the usual moves are a smaller vanity, a corner sink, or a shower in place of the tub, in roughly that order of cost.
Does this account for the shower door or the vanity doors?
No, and both are worth checking by hand. A hinged shower door swings into the room exactly as the entry door does and can conflict with the toilet or the vanity, which is one reason sliding and pivot doors are common in tight bathrooms. Vanity doors and drawers project when open and the space in front of the vanity has to absorb that as well as the person standing there. The front clearance figure here measures to the fixture face, so subtract the drawer projection yourself if the drawers are deep. Anything that projects into the room and is not a fixture, such as a radiator or a towel rail, can be entered as an extra line with its own width and depth so the door swing check sees it.