Toilet Rough-In Sizes: How to Measure 10, 12 and 14 Inch

What rough-in means

Rough-in is the distance from the finished wall to the centre of the closet bolts that hold your toilet down. It tells you how far the waste pipe sits from the wall, and it decides which toilets will physically fit.

Three sizes exist: 10 inch, 12 inch and 14 inch. Around 90% of American bathrooms are 12 inch. Ten-inch rough-ins usually turn up in older homes and powder rooms; 14 inch is rare and normally the result of a remodel.

How to measure your rough-in

1. Find the bolt caps at the base of your toilet, where it meets the floor.
2. Measure from the wall behind the tank to the centre of those bolts.
3. Measure to the finished wall — not the baseboard. If a baseboard is in the way, measure to the wall above it.
4. If your toilet has four bolts, use the back pair.

You do not need to remove the toilet. If the number lands within half an inch of 10, 12 or 14, that is your rough-in.

Getting an odd number

A reading of 11 or 13 inches usually means you measured to the baseboard rather than the wall, or the original installation was slightly off. Toilets are made to three sizes only. If you genuinely measure 11 inches, order the 10-inch model — a toilet can sit further from the wall than its rough-in, but never closer.

Popular at each rough-in size

12 inch

TOTO Drake Two-Piece Toilet - Universal Height, Elongated

The standard size, and our best-selling toilet.

$514.54

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10 or 14 inch

TOTO Aquia IV Two-Piece Toilet - Universal Height

Unifit adapter available for both alternatives.

$1,089.00

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Which TOTO series offer 10 and 14 inch

This is where most buying guides stop being useful. "Most toilets offer an adapter" is not true, and the ranges differ more than you would expect. We checked every TOTO model we stock against TOTO's own specification sheets. Here is what they actually offer.

The Nexus exception is worth knowing

The Nexus is one of TOTO's most popular skirted ranges, and it is the one series where a 10-inch rough-in is simply not available. Every Nexus model takes a 12-inch as standard and a 14-inch adapter as an option. If your bathroom is 10 inch, the Nexus is out — the Aquia IV or Carlyle II are the closest alternatives that do offer it.

The two ways a non-12-inch toilet works

Unifit adapter

Most TOTO skirted one-piece and dual-flush ranges use TOTO's Unifit system. You buy the standard toilet plus an adapter that changes the outlet position. The adapter is fitted during installation and cannot be added later without lifting the toilet.

The part numbers differ by series and are not interchangeable — a Unifit adapter for an Aquia IV will not fit a Carlyle II. Order the adapter with the toilet and we will match the correct part to your model.

A separate model

The Drake and Drake Transitional work differently. There is no adapter. Instead TOTO makes a separate 10-inch version of certain models, marked with .10 in the model number. It is a different toilet, ordered as its own item.

One consequence catches people out: a 10-inch Drake fits a 10-inch rough-in only. It will not sit correctly on a standard 12-inch drain.

Common mistakes

• Measuring to the baseboard instead of the finished wall.
• Measuring to the front bolts on a four-bolt toilet.
• Assuming every series offers 10 and 14 inch — several offer neither.
• Ordering a Unifit adapter from a different TOTO series.
• Buying a .10 model for a 12-inch bathroom.

Frequently asked questions