How the Bathroom Fixture Clearance Checker works

Two model codes set minimum clearances around bathroom fixtures in houses, and they do not agree. This tool checks your measurements against one of them at a time, the one you pick, and never mixes the two.

Where the IRC figures come from. Section R307.1 of the 2021 IRC says fixtures are to be spaced as its Figure R307.1 shows and as Section P2705.1 requires. P2705.1 gives the side, centre-to-centre and front distances for water closets, lavatories and bidets in words. Section P2708.1 gives the shower area and smallest dimension, and P2708.1.1 the width of the opening. The 24 in in front of the shower opening is printed only in the figure, which is an image; it was read from the image, along with the points the figure measures from.

Where the UPC figures come from. Section 402.5 of the 2024 UPC gives the side and centre-to-centre distances for a water closet or bidet and the clear space in front of a water closet, lavatory or bidet. Section 408.7 gives the shower area and the 30 in circle, and Section 408.6 the 22 in door opening. For a rectangle, holding a 30 in circle is the same as having a shorter side of at least 30 in.

Where each distance is measured. Both codes measure the side distance from the centre of the fixture, not its edge. Neither says in words where the space in front starts; the IRC figure draws it from the front of the bowl and the front of the lavatory, and this tool uses the front edge of the fixture under both codes. Shower sizes are finished inside dimensions in both codes, taken at the height of the top of the threshold and kept up to 70 in above the drain. The IRC leaves valves, shower heads, soap dishes and grab bars out of that measurement; the UPC leaves out the same things and shelves.

Finished surfaces. For the toilet and lavatory distances neither code says whether a wall is measured at the studs or at the tile. This tool checks finished-surface distances, because that is the room the inspector sees, and it subtracts nothing for you. If your walls are still bare framing, take the thickness of the board and tile still to come off each measurement before you enter it: once for a distance to one wall, a shower wall or a curb, twice for a distance between two of them. The tool asks you to confirm that your figures are finished-surface distances, with nothing filled in; until you answer Yes the result is not a pass, and No is refused with that instruction. A clearance that passes with under 1 in to spare is named in the result.

What is on each side. For each side of a toilet or lavatory you choose what is nearest: a wall or partition, a tub or shower, a sink, a cabinet with no sink, another toilet or bidet, or nothing within 36 in. Beside a toilet the sink answer is a sink on its own or one set in a vanity or cabinet. Beside a lavatory it is another sink in its own vanity, measured to the side of that vanity; a second basin in the same top, or a sink with no vanity, is a separate answer, measured to the edge of that basin. Beside a lavatory a tub or shower is two answers as well: a shower's wall, glass panel or door, including one standing on a tub, or the rim of a bathtub with none of those on it. That one answer decides which rules run. Nothing is filled in for you, and until you answer the result is not a pass. An open side gets no line at all; the 36 in is measured from the centre of the fixture and is this tool's own threshold, chosen to be larger than any side figure in either code.

Exceptions. The IRC exception for a shower with a smallest dimension of 25 in is applied as worded: it needs 1,300 sq in, and below 25 in nothing passes. The IRC exception for fold-down seats (the required area must still be there with the seat folded up) has no entry of its own: measure with the seat up. The UPC exception for a shower receptor at least 30 in wide and 60 in long overall is applied from your answer to that question: where the inside size is under a minimum, Yes replaces the area and circle lines with one marked "Exempt", No fails them, and no answer is not a pass. A Yes beside a shower whose longer inside side is under 48 in is sent back as a question, since no receptor that long could be that short inside; that figure is this tool's own check, not the code's. The UPC exception for showers designed to ICC A117.1 is not checked. The UPC also says paper dispensers and accessibility grab bars are not obstructions.

Rounding. Figures are rounded away from a pass: a distance or area down, a shortfall up, so a value under its minimum is never printed as equal to it.

Readings this tool takes where the wording leaves room.

• The IRC text names a side wall, partition or vanity for the 15 in, and its figure draws the same distance from a water closet or bidet to the edge of a tub. Beside a toilet this tool also applies it to a cabinet with no sink and to the nearest edge of another fixture; those lines say they are this tool's reading. The UPC says side wall or obstruction, which covers all of them.
• The same sentence covers the lavatory, so beside a lavatory a side wall, a partition, a vanity and (read as a vanity) a cabinet closer than 15 in to its centre fail, exactly as beside a toilet. So does a shower's wall, glass panel or door, which this tool reads as a side wall or partition. The rim of a bathtub, the edge of a second basin in the same top or of a sink with no vanity, and the bare edge of a toilet or bidet are not in that list, and the figure shows the 15 in to a tub only from a water closet or bidet. Those are shown as "Ask", this tool's reading for you to confirm, and never as a fail. Until you say what is beside the lavatory that line is not run.
• The IRC sentence asks for 30 in centre to centre between adjacent fixtures and does not say which fixtures. It is read here as toilets, bidets and lavatories, the three the sentence is about, and not tubs or showers. Between two toilets or bidets, or two lavatories, a shortfall is a fail. Between a toilet and a lavatory the figure draws the pair side by side with only the 15 in dimension, so a shortfall there is shown as "Ask", and when it is the only thing short the result says the layout passes unless your inspector applies the 30 in to that pair. A toilet 15 in from the edge of a narrow vanity is the usual case.
• Under the UPC the centre-to-centre rule is to a "similar fixture", which this tool reads as another toilet or bidet. A sink beside a toilet is treated as an obstruction under the side rule instead.
• The space in front of the shower opening is measured from the outside face of the shower, because the figure does not say where it starts.
• A built-in shower bench is measured to its face, because neither list of things left out of the measurement includes seats.

Editions. The 2024 IRC renumbers the section and figure to R327.1 with the same dimensions, and its P2705.1 and P2708.1 carry the same figures; so does Chapter 27 of the 2018 edition. The 2021 UPC has the same figures as the 2024 edition one section number earlier for showers.

Scope. These are the ordinary minimums for one- and two-family dwellings. They are not accessible design clearances: the ADA Standards and ICC A117.1 call for larger spaces and are not checked here. Door swings (the IRC requires hinged shower doors to open outward), ceiling height over fixtures, ventilation, glazing, tub sizes and drain or vent sizing are not covered, and only rectangular showers are checked. States and cities adopt these codes with their own amendments, which govern: one 2018 adoption read for this tool, for example, lets a lavatory in a remodel sit 12 in from its centre to a side wall. Check which code and edition your jurisdiction enforces.

This tool cannot be published unless it reproduces every example below. 1 is copied from a published source. 31 were worked by hand from the cited rule.