How much clear floor does a bathroom fixture need in front of it?

Published planning guidelines ask for 30 inches (762 mm) of clear floor in front of a toilet, a tub and a lavatory. The figure quoted from the model code text is 21 inches (533 mm), and it is required in many US jurisdictions. What applies where you live is decided by your building department.

Why do bathroom dimensions online contradict each other?

Because the figures come from three kinds of document that get quoted without labels: a published planning guideline from an industry body, a minimum in a model code text adopted in many US jurisdictions, and a dimension one manufacturer publishes for one of its own products. Each is correct about a different question.

What has to be decided before a bathroom wall is closed?

Valve height and valve depth, the fan size and where its duct terminates, the blocking for grab bars, a niche, a wall hung vanity and the shower glass jamb, and the waterproofing height. All of them are fixed across the three days between framing and drywall, and none can be changed afterwards without opening the wall.

Does a homeowner need to know rough-in figures?

The figures themselves belong to the trades and to the manufacturer sheets. What a homeowner needs is the questions and the timing, because a valve height taken from a generic chart rather than the sheet for the trim that was bought is a mistake nobody notices until the trim will not sit on the tile.

Bathroom planning, and which kind of figure each number is

Bathroom planning is decided in two stages. On paper, the clearances: published planning guidelines ask for 30 inches (762 mm) of clear floor in front of every fixture, where the model code text quoted alongside sets 21 inches (533 mm), required in many US jurisdictions, verify locally. In the room, the rough-ins: valve heights and depths, duct routes and blocking, all of which are fixed before the walls close.

Every bathroom number belongs to one of three documents

Search for any bathroom dimension and several figures come back, unlabeled and disagreeing. They come from three different kinds of document, and almost every bad bathroom decision starts with treating one kind as another.

A published planning guideline is a recommendation from an industry body. Nobody inspects it and no building department enforces it. It is the size at which a fixture stops being a compromise, and it is what a designer works to.
A model code figure is text from a code that many US jurisdictions have adopted. It is a minimum, deliberately small, and what applies where you live is decided by your building department, through your contractor.
A manufacturer dimension is the figure one company publishes for one of its own products. It decides where that exact model sits, it changes from model to model, and the sheet that counts is the one in the box.

A bathroom built entirely to the code figures is one in which every dimension is the least anybody was willing to write down. Knowing which figure you are sitting at is a decision. Averaging them without knowing is not.

Half of a bathroom is decided before anyone sees tile

The clearances are settled on a drawing, which can be changed. The other half is settled in three days between framing and drywall, and it cannot.

Valve height and depth, the fan and where its duct comes out of the building, the blocking for a grab bar, a niche or a wall hung vanity, and the waterproofing height are all fixed in those days. None is work a homeowner carries out. All are questions a homeowner can ask.

Look, photograph and ask. On the day the wall is open, that is the whole of the homeowner job, and it is worth more than it sounds.

The order these get decided in

Clearances first, because they decide whether the fixtures fit at all. Then the fixtures, because a tub rough opening and a toilet rough-in are manufacturer figures that have to reach the person framing the wall. Then the rough-ins, because valve depth depends on a tile selection people tend to make last.

That last dependency is the one to carry away. Changing the tile late changes the thickness of the finished wall, and that thickness is what a valve was set for weeks earlier, behind a wall that is now closed.

What size bathroom fan do you need

One industry body publishes two methods for sizing a bath fan, one for rooms up to 100 square feet and a different one above it, and the model code adds a minimum underneath both.

How much space you need around a toilet, a shower and a vanity

Almost every clearance in a bathroom has two published figures, a planning guideline and a smaller figure from a model code. This page prints them in the same table and keeps them labeled.

What to check before the walls close

The open wall is not one moment, it is three, they belong to three different trades, and a question asked on the wrong day is a question asked too late.

Shower valve height and depth, and why the depth is the one that comes back

Height is the number everybody discusses. Depth is the number that comes back, and the proof is that manufacturers sell handle extension kits in named thickness ranges for exactly this failure.