Toilet Rough-In: 10 vs 12 Inch – How to Measure and Which Smart Toilets Fit
How to measure your toilet rough-in, what happens if you buy the wrong size, and which smart and bidet toilets are made for a 10-inch or 12-inch rough-in – with current prices.
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Short answer: Measure from the finished wall behind the toilet to the center of the floor bolts. About 12 inches means a 12-inch rough-in – the size most smart toilets are made for. About 10 inches means you need a 10-inch model, and the choice is much smaller: at HOROW, only the T37 smart toilet ($1,269) and the non-electric T30-NE ($539) are listed for it.
Prices are from HOROW’s US store on November 4, 2026. Always confirm the rough-in on the specific product page or installation manual before ordering.
How to measure rough-in
- Find the floor bolts at the base of the toilet (usually under caps on each side).
- Measure from the wall surface behind the toilet – not from the baseboard or trim – to the center of one bolt.
- Match it to a standard size: a reading close to 12 inches is a 12-inch rough-in; close to 10 inches, a 10-inch rough-in. Some older homes have a 14-inch rough-in.
- No toilet installed? Measure to the center of the drain opening (the closet flange).
What happens if you get it wrong
| Your rough-in | Toilet made for | Result |
|---|---|---|
| 10” | 12” | Doesn’t fit – the back of the toilet hits the wall |
| 12” | 10” | Fits, but leaves about a 2-inch gap behind the toilet |
| 12” | 12” | Correct fit |
Swipe to see the full table →
Getting this wrong is costly with smart toilets because returns usually require the toilet to be uninstalled and in its original packaging – HOROW’s 90-day return policy works that way.
Smart and bidet toilets by rough-in (HOROW, Nov 4, 2026)
| Rough-in | Model | Type | Price |
|---|---|---|---|
| 10” | T37 | Tankless smart toilet, heated bidet seat, auto lid | $1,269 |
| 10” | T30-NE | Non-electric bidet toilet, ADA height | $539 |
| 12” | T16 | Tankless smart toilet | $559 |
| 12” | T33 | Tank + pump, ADA comfort height | $799 |
| 12” | T03Pro | Tank + pump | $899 |
| 12” | T05 | Tank + pump, dryer | $949 |
| 12” | T36 | Pump-assisted, black | $990 |
| 12” | T38 | Built-in tank, dryer, mood light | $999 |
| 12” | T38P | Tank + pump, ADA comfort height | $1,299 |
| 12” | T39 | Tank + pump, ADA comfort height | $1,399 |
| 12” | X70 | Tank + 100W pump | $1,599 |
| 12” | T30 | Non-electric bidet toilet | $499 |
Swipe to see the full table →
If your rough-in is 10 inches and you don’t want a full smart toilet, a bidet seat on a standard 10-inch toilet is the cheaper route – see smart toilet vs bidet seat.
See HOROW's 10-inch rough-in T37Other fit checks
- Floor vs wall outlet: the toilets above are floor-outlet models; wall-hung toilets such as HOROW’s G10 need an in-wall carrier instead.
- Power: electric smart toilets need an outlet near the toilet.
- Seat height: ADA comfort-height models (T33, T38P, T39, T30-NE) suit taller users and people with limited mobility.
For every HOROW model side by side, see our HOROW smart toilet review.
Adding a toilet below the drain line instead? See upflush toilets.
Key takeaways
- Rough-in is the distance from the finished wall behind the toilet to the center of the drain – in practice, to the center of the floor bolts.
- Measure from the wall surface, not from the baseboard, and round to the nearest standard size (10, 12 or 14 inches).
- Most smart toilets are built for a 12-inch rough-in; of HOROW's in-stock range, only the T37 smart toilet ($1,269) and the non-electric T30-NE ($539) are listed for 10 inches.
- A 12-inch toilet won't fit a 10-inch rough-in (it hits the wall); a 10-inch toilet on a 12-inch rough-in leaves a gap behind the tank.
Frequently asked questions
How do I measure toilet rough-in?
Measure from the finished wall behind the toilet (not the baseboard) to the center of one of the bolts holding the toilet to the floor. A reading near 12 inches means a 12-inch rough-in; near 10 inches, a 10-inch rough-in.
Can I put a 12-inch rough-in toilet on a 10-inch rough-in?
Generally no – the tank or back of the toilet would hit the wall. You'd need a toilet made for a 10-inch rough-in or a plumbing change to move the drain.
Which smart toilets fit a 10-inch rough-in?
Fewer models are made for it. At HOROW, the T37 smart toilet ($1,269) and the non-electric T30-NE bidet toilet ($539) are listed for a 10-inch rough-in (prices November 4, 2026).
What is the most common toilet rough-in?
12 inches is the size most smart toilets are made for – in HOROW's range, every in-stock smart toilet except the T37 lists a 12-inch rough-in or doesn't state one.