Toilet rough-in is the single measurement that decides whether a toilet will fit. It is the distance from the finished wall behind the toilet to the centre of the drain pipe in the floor, and in Canada it is almost always 12 inches. Older homes, basements and tight condo layouts sometimes have a 10-inch rough-in, and a few pre-1970s houses have 14 inches. Buy a toilet for the wrong rough-in and it either will not connect to the drain or sits with a gap behind the tank you can put a hand through.
This guide shows you how to measure it in under a minute, explains what fits what, and covers the other clearances your plumber and the building code care about: side space, front space, supply line position and seat height.
Quick answer
- Rough-in = finished wall to centre of the flange bolts (the drain). Ignore the baseboard.
- 12" is standard and fits nearly every toilet sold in Canada.
- 10" needs a toilet made for 10" rough-in; a standard 12" model will not fit.
- 14" takes a 12" toilet with a 2" gap behind the tank, or a 14" model if you want it flush to the wall.
- Also allow 15" from the toilet centre to any side wall or vanity and 21" of clear floor in front (24" is comfortable).
How to measure toilet rough-in
If the old toilet is still in place you do not need to remove it. If it is already out, measure to the centre of the flange itself.
- Find the closet bolts. They are the two bolts at the base of the toilet, one each side, usually under plastic caps. They sit on the centreline of the drain.
- Measure from the wall to the centre of a bolt. Use the finished wall, meaning the drywall or tile surface, not the baseboard. If a thick baseboard is in the way, measure to the baseboard and add its thickness.
- Round to the nearest standard size. 11-1/2" to 12-1/2" is a 12" rough-in. 9-1/2" to 10-1/2" is 10". 13-1/2" to 14-1/2" is 14".
- If the toilet has four bolts (some older models), measure to the rear pair.
- No toilet installed? Measure from the finished wall to the centre of the round flange opening in the floor.
Renovating and adding tile or a thicker wall behind the toilet? Measure from where the new finished surface will be. A 3/4-inch layer of cement board and tile turns a 12-1/2" rough-in into 11-3/4", which still works for most 12" toilets but not all. Check the product’s minimum rough-in on its spec sheet.
10-inch vs 12-inch vs 14-inch: which toilets fit
| Your rough-in | Where it is found | What fits |
|---|---|---|
| 12" (305 mm) | Every home built since the 1970s; the North American standard | Almost every one-piece and two-piece toilet on the market. Everything in our toilet collection unless the listing says otherwise. |
| 10" (254 mm) | Pre-1970s houses, finished basements, condos where the drain was placed close to the wall | Only toilets sold as 10" rough-in. Toto and several other brands make 10" versions of popular models; the bowl is the same, the tank is shallower. A 12" toilet will not reach the drain. |
| 14" (356 mm) | Some older houses and a few custom builds | A 12" toilet fits with roughly a 2" gap behind the tank. A 14" model closes the gap. Some skirted one-piece toilets adapt to 10–14" with an offset kit. |
| Wall-hung | Modern renovations | No floor rough-in at all. The drain exits through the wall into an in-wall carrier, so the floor stays clear. See wall-mount toilets. |
One common mistake: a 10-inch toilet does fit a 12-inch rough-in, with a 2-inch gap behind the tank. It is not ideal, but if you bought the wrong one, it works. The reverse does not.
Side and front clearances
Rough-in gets a toilet onto the drain. Clearances make it usable and code-compliant. The National Building Code and provincial codes in Ontario, Quebec, BC and Alberta all work from the same numbers.
| Clearance | Code minimum | Comfortable |
|---|---|---|
| Toilet centreline to side wall, vanity or tub | 15" (380 mm) each side | 18" |
| Total width of the toilet space | 30" | 36" |
| Clear floor in front of the bowl | 21" (some jurisdictions 24") | 30" |
| Front of bowl to a door swinging inward | Door must clear the bowl | Or hang the door to swing out |
The front clearance is where bowl shape matters. An elongated bowl is about 18-1/2 inches from the bolts to the front rim; a round-front bowl is about 16-1/2 inches. In a small powder room those 2 inches are often the difference between passing and failing the front-clearance check.
Water supply rough-in
The shut-off valve on the wall needs to land beside the tank, not behind it. Standard placement is 6 inches to the left of the toilet centreline (facing the toilet) and 6 to 8 inches above the finished floor. Most tanks connect with a 3/8-inch compression fitting on a braided steel supply line. If you are adding a bidet seat or an integrated smart toilet, that same valve feeds the seat through a T-fitting, and you will also need a GFCI outlet within about a metre.
Toilet height: standard vs comfort height
Rough-in is horizontal; height is the other number people confuse it with. Height is measured from the floor to the top of the seat.
| Height | To top of seat | Best for |
|---|---|---|
| Standard | 14-1/2"–16" | Children, shorter users; squat-friendly posture |
| Comfort / universal / ADA height | 17"–19" | Adults, anyone with knee or hip issues; the same height as a chair |
| Wall-hung, adjustable | Set at install, typically 15"–19" | Whoever lives there; the carrier sets it |
One-piece vs two-piece: does rough-in differ?
No. Both come in 12-inch as standard and the measuring is identical. The differences are elsewhere:
- Two-piece (separate tank and bowl, like the Toto Drake) costs less, ships in two lighter boxes, and lets you replace a cracked tank without replacing the bowl. The seam between tank and bowl is a place grime collects.
- One-piece has no seam, so it wipes clean in one pass and looks lower and cleaner. It is heavier to carry up stairs and costs more to ship.
- Skirted versions of either hide the trapway behind a smooth ceramic skirt. They are the easiest to clean and usually adapt to 10–14" rough-ins with the manufacturer’s offset flange kit.
Three toilets that cover the common cases
Dual-Flush One-Piece, 12" rough-in
$208.50
Elongated, soft-close seat included, no seam to clean
Toto Drake Bowl + Tank
$218 + $167
Two-piece, 1.28 gpf, universal height, CeFiONtect glaze
Duravit D-Neo Wall-Hung Set
$1,000
Rimless bowl, in-wall tank and carrier; no floor rough-in
Wall-hung toilets: the rough-in is in the wall
A wall-mounted toilet ignores the floor drain entirely. The bowl bolts to a steel carrier frame hidden inside the wall, and the tank sits inside the same frame behind an actuator plate. The drain exits horizontally through the wall. What you need instead of a floor rough-in:
- A wall that is either 2×6 framed or 2×4 furred out to about 6 inches to hold the carrier and tank.
- The drain rerouted to exit at the carrier’s outlet height, roughly 8–9 inches above the finished floor.
- A plumber, because this is a renovation-stage job, not a swap.
The payoff is a completely clear floor, a seat height you choose, and a toilet that projects 21–22 inches from the wall instead of 28–30, which is why they are popular in small Toronto and Montreal condos. See the full range of wall-mount toilets, in-wall tanks and actuator plates.
Replacing a toilet: a checklist before you order
- Rough-in measured from the finished wall: ____ inches.
- Bowl shape that clears the door and gives 21" in front: round or elongated.
- Side clearance of at least 15" from centre to each side.
- Supply valve position: 6" left of centre, 6–8" up. If it is behind where the new tank will sit, plan to move it.
- Seat height you want: standard or comfort.
- Flange condition. A cracked or corroded flange gets replaced while the toilet is off; budget $30 for the part and an extra hour of plumber time.
- Outlet nearby if you intend to add a bidet seat.
Frequently asked questions
What is the standard toilet rough-in?
Twelve inches, measured from the finished wall to the centre of the drain flange. Nearly every home built in Canada since the 1970s uses it, and nearly every toilet is made for it.
Can I put a 12-inch toilet on a 10-inch rough-in?
No. The tank will hit the wall before the bowl reaches the drain. You need a toilet made for 10-inch rough-in, or a skirted model with a manufacturer’s offset kit rated for 10 inches.
Can I put a 10-inch toilet on a 12-inch rough-in?
Yes. It fits and works normally; there will be about a 2-inch gap between the tank and the wall.
How do I measure rough-in with the toilet still installed?
Measure from the finished wall to the centre of one of the two closet bolts at the base of the toilet. Do not measure from the baseboard; if it is in the way, add its thickness.
Does a wall-hung toilet need a floor rough-in?
No. The drain goes through the wall into an in-wall carrier, so the floor is clear. It needs a deeper wall and a plumber to reroute the drain.
How much space does a toilet need from the wall on each side?
Fifteen inches from the toilet centreline to any side wall, vanity or tub is the code minimum, giving a 30-inch-wide space. Eighteen inches each side is comfortable.
Find a toilet that fits
All toilets · One-piece toilets · Wall-mount toilets · Smart toilets · Bidet seats. Every product page lists rough-in, bowl shape and seat height. Free delivery on orders over $600 in Ontario.
