Bathroom layout checker

Bathroom layout checker#

Enter the room and the fixtures. The calculator checks every clearance against the IRC minimums and the more generous NKBA planning guidelines, and reports which ones fail.

Inches Centimetres

Room width in

Room length in

FixturesToilet, basin and bathToilet, basin and showerToilet and basin onlyToilet, double basin, shower and bath

Door width in

Toilet centre line from the nearest wall in

Clear space in front of the toilet in

Enter your measurements above.

IRC figures are legal minimums for new work in most US jurisdictions. NKBA figures are planning guidelines and are the ones to design to where the room allows.

Nothing you type leaves your browser: the maths runs on this page, and no values are stored or sent anywhere.

Enter the room, the set of fixtures, the door width and the two toilet dimensions. The checker returns the floor area, tests the room against a workable minimum for that fixture set, and grades each clearance against the IRC minimum and the NKBA guideline. It runs in your browser as you type: nothing is stored and nothing is sent anywhere. It is a planning tool, not a plan check.

The three clearances it tests, and where they come from#

Toilet centre line. Measured from the centre of the bowl to the nearest wall, fixture or door on either side, not from the edge of the pan. The IRC sets 15 in (38 cm) as the minimum, so the fixture needs 30 in (76 cm) of wall between obstructions. The NKBA planning guidelines ask for 18 in (46 cm), giving 36 in (91 cm) of wall. The checker passes you at 18, warns between 15 and 18, and fails below 15.

Clear space in front. Measured from the front rim of the pan to whatever is opposite, whether that is a wall, a vanity or a bath. The IRC allows 21 in (53 cm) and the NKBA guideline is 30 in (76 cm). Same three-way verdict.

Door width. Compared against 32 in (81 cm), the clear width an accessible route needs. Domestic bathroom doors are routinely 24 to 28 in (61 to 71 cm), so most rooms get a warning here rather than a pass. The distinction between a leaf width and a clear width is set out in door sizes, swings and the space they need, and it costs about 2 in.

All three are measured to finished surfaces, which means after tiling. Half an inch of tile and adhesive on each of two walls turns a 30 in gap into 29 in, and the number the inspector reads is the finished one. The full set of bathroom figures, including the ones this tool does not test, is in bathroom fixture clearances.

The arithmetic, worked on a 5 x 8 ft bathroom#

Take the default: a 60 x 96 in room, a toilet, basin and bath, a 28 in door, an 18 in centre line and 24 in in front.

1. Area. 60 x 96 = 5,760 sq in. Divide by 144: 40.0 sq ft, or 3.7 m2.
2. Fixture set. A toilet, basin and bath needs at least 60 x 84 in. The short side is 60 and the long side is 96, so both clear. Pass.
3. Centre line. 18 in meets the NKBA guideline. Pass.
4. Front clearance. 24 in is above the IRC 21 in but below the guideline 30 in. Warning.
5. Door. 28 in is below 32 in. Warning.
6. Door swing. A quarter circle of radius 28 in has an area of pi x 28 x 28 / 4 = 616 sq in, which is 4.3 sq ft (0.40 m2).

That last figure is the one that changes decisions. The swing is 11 per cent of a 40 sq ft room, and it is not floor you can use for anything else.

IRC against NKBA, side by side#

The first column is enforceable and the second is not. That is the whole difference: the IRC exists to stop a bathroom being unusable, and the NKBA guidelines exist to make it comfortable. Where the two disagree, the site's working recommendation is to design to the guideline and treat the code figure as the point at which you stop cutting. The rest of the codes and reference works are described in standards, codes and sources.

What the room minimums assume#

The full bathroom figure is set by the bath: a standard tub is 60 x 30 in (152 x 76 cm), so a 60 in short side is the bath length exactly and leaves nothing for a wall thickness or an out-of-square room. Shower sizes are the same argument in a smaller space, and are set out in shower sizes and clearances. Worked plans at each of these footprints are in small bathroom layouts that work, and the room-by-room minimums for the rest of the house are in standard and minimum room sizes.

Where judgement replaces the arithmetic#

The checker compares your short side against the minimum short side and your long side against the minimum long side, independently. A room can pass both and still be unusable, because it says nothing about where the door is, whether the window is over the bath, or whether the soil stack is on the wrong wall. A 48 x 78 in shower room with the door in the middle of a long wall is a different room from the same rectangle with the door in a corner.

Two more judgement calls sit outside the maths. The first is whether to build to the guideline or the minimum: in a second bathroom used by one person, 21 in in front of the toilet is a reasonable trade for a wider vanity, and the vanity sizes that follow are in vanity heights and sizes. The second is who uses the room. Ageing users, a wheelchair, or an adult helping a child all need clear floor space the checker never asks about, which is set out in accessible bathroom dimensions.

What the checker deliberately does not do#

• It does not lay out the fixtures or check them against each other. Only the toilet dimensions you type are tested.
• It does not check basin, bath or shower clearances, nor the height of anything.
• It does not test the 60 in (152 cm) turning circle an accessible bathroom needs, or reach ranges to a control.
• It does not know about ventilation, windows, or the electrical zones around a bath and shower, which have their own rules in bathroom electrical zones and clearances.
• It does not consider mirror or light positions, covered in bathroom mirror and lighting heights.
• It does not apply your local amendments to the IRC, and it knows nothing about UK, EU or Australian requirements.

The rest of the interior dimension calculators handle the pieces this one leaves alone.