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Short answer: Measure from the seat mounting holes to the front of the bowl: about 18.5 inches means elongated, about 16.5 inches means round. Then check TOTO’s clearances: at least 2 inches from the tank to the mounting-hole centers, about 5-1/2 inches between hole centers, and 8 inches of flat bowl surface.
How we compare: every spec in this article comes from official manufacturer specifications and manuals (starting with TOTO USA’s official documentation), all listed under Sources below. We don’t run hands-on tests, and if a spec isn’t published, we say so. Last updated: October 2026.
I live in Japan, where Washlet-style seats are standard in most homes. In the US, though, the fit question comes first because toilets vary so much.
Everything below comes from TOTO USA’s official Washlet fit chart and comparison pages. I haven’t installed these seats myself.
Step 1: Round or Elongated?
| Bowl type | Mounting holes to front of bowl (TOTO) |
|---|---|
| Round | About 16-1/2 in (420 mm) |
| Elongated | About 18-1/2 in (470 mm) |
Measure from the center of the seat bolt holes to the front lip of the bowl. Buy the matching shape. Many TOTO models come only in elongated.
Step 2: TOTO’s Installation Clearances
From TOTO’s fit chart, “Washlet Installation Requirements”:
| Check | TOTO requirement |
|---|---|
| Front face of tank to center of mounting holes | Minimum 2 in (50 mm) for S7A, S7, S5, S2, and KS6 |
| Distance between centers of seat mounting holes | About 5-1/2 in (140 mm) |
| Center of toilet to edge of flat bowl surface | Minimum 8 in (203 mm) |
| Power cord length | 3.9 ft (1.2 m) on most models in the chart |
TOTO also warns that “some styles of toilets may not allow the WASHLET to fit properly due to certain contours where the tank meets the bowl.” Toilets with a curved or sculpted joint between tank and bowl are the most likely to cause trouble.
Don’t forget the outlet. With a cord of about 3.9 ft, you need an outlet near the toilet. Check TOTO’s installation guide for electrical requirements.
Step 3: Model Sizes (From TOTO’s Fit Chart)
| Model | Shape | Product size (from TOTO chart) | Rated power |
|---|---|---|---|
| S7A (SW4736/SW4734) | Elongated | 23-3/8” L x 17-5/8” W x 6-1/4” H | 1290 W |
| S7 (SW4726/SW4724) | Elongated | 23-3/8” L x 17-5/8” W x 6-1/4” H | 1290 W |
| S5 (SW3446) | Elongated | 15” W x 21” D x 5-1/2” H | 1271 W |
| S5 (SW3445) | Round | Size not clearly readable in chart* | 1273 W |
| S2 (SW3346) | Elongated | 18-7/16” W x 21” D x 5-1/2” H | 1273 W |
| S2 (SW3345) | Round | Size not clearly readable in chart* | 1273 W |
| KC2 (SW3024) | Elongated | 18-5/8” W x 20-7/8” D x 5-3/4” H | 403 W |
| KS6 (SW3946) | Elongated | 15-1/4” W x 20-13/16” D x 5-1/2” H | 1278 W |
| K300 (SW3036R) | Elongated | 15-1/8” W x 20-7/8” D x 5-3/16” H | 1274 W |
| A2 (SW3004) | Elongated | 18-5/8” W x 20-7/8” D x 6-5/8” H | 287 W |
S5 and S2 sizes: the PDF’s columns don’t line up cleanly, so confirm these on each model’s TOTO spec sheet. *The PDF’s layout makes the round-model dimensions hard to read reliably, so I’ve left them out. Check TOTO’s spec sheet for each round model. TOTO notes that the KC2 and K300 are e-commerce only products.
Where to buy: TOTO A2 SW3004 · TOTO S2 SW3346 · TOTO S5 SW3446 · TOTO S7 SW4726
Step 4: Check TOTO’s Compatibility Chart for TOTO Toilets
If you own a TOTO toilet, TOTO’s fit chart includes a compatibility grid. It covers one-piece, two-piece, and wall-hung TOTO toilets, such as the Drake, Ultramax, Aquia IV, and Nexus lines, matched against Washlet models. Some combinations need an extension kit:
- THU9090R (marked * in the chart)
- 9AU321-A (marked ** in the chart)
Open the PDF and find your toilet’s name to confirm.
Common Fit Problems
- Wrong shape: an elongated seat on a round bowl will overhang the front.
- Tank too close to the holes: under 2 inches of clearance can block the seat’s base for the models TOTO lists.
- Narrow flat surface: under 8 inches from center can keep the seat from sitting flat.
- No nearby outlet: a cord of about 3.9 ft won’t reach far.
Once you know your bowl shape, compare models: TOTO A2 vs C2 for entry seats, or TOTO S7 vs S7A for the elongated-only S line.
Fit, from the Japan Side
Bidet seats are standard in Japan, and TOTO Japan approaches fit the same way it does in the US: you check the toilet’s measurements first. For its domestic Washlet Apricot, TOTO Japan says installing it on another maker’s toilet requires checking the bowl dimensions against its installation conditions, and part numbers differ by toilet type. That’s the same logic as the round vs elongated check above. Japanese-market Washlets are sized for Japanese toilets and 100 V power, so measure for the US model you’re actually buying rather than a Japanese spec sheet.
Japanese reviewers of the current Apricot F3 on Kakaku.com often mention quieter operation and easier cleaning than older units; complaints include a motion sensor that may not react depending on where the door is, and a strongest spray some found weaker than before. (Third-party reviews, not our own testing.)
Frequently Asked Questions
How do I know if my toilet is round or elongated?
Measure from the mounting holes to the front of the bowl. About 16.5 inches is round, and about 18.5 inches is elongated, per TOTO.
Does a TOTO Washlet fit non-TOTO toilets?
TOTO says a Washlet “will fit most North American toilets,” but toilets with unusual contours where the tank meets the bowl may not work. Check the clearances above.
What is the minimum clearance from the tank?
2 inches (50 mm) from the front of the tank to the center of the mounting holes, for the S7A, S7, S5, S2, and KS6, according to TOTO’s fit chart.
Do I need an outlet next to the toilet?
Yes. Washlets are electric, and the chart lists cords of about 3.9 ft (4 ft for the S7 and S7A).
What is Washlet+?
TOTO’s Washlet+ pairs a specially designed TOTO toilet with a Washlet+ seat, with no visible hoses or cords. It requires a compatible TOTO toilet.
Which models come in round?
In TOTO’s current fit chart, the S5 (SW3445) and S2 (SW3345) are listed as round. The other models in the chart are elongated.
Related comparisons
- TOTO Washlet A2 vs C2: Is the C2 Worth the Upgrade?
- TOTO Washlet C2 vs C5: What’s Actually Different?
- TOTO Washlet C5 vs S7: Tank or Instant Heating?
- TOTO Washlet S7 vs S7A: Is the Auto Lid Worth It?
Sources
- TOTO USA, WASHLET Fit Chart (PDF; sizes, clearances, compatibility): https://www.totousa.com/filemanager_uploads/product_assets/OwnersManual/Washlet-Fit-Chart.pdf
- TOTO USA, WASHLET Bidet Seats (round vs elongated, Washlet+): https://www.totousa.com/washlet-new
- TOTO Japan: Washlet Apricot product page (jp.toto.com): https://jp.toto.com/products/toilet/apricot/
- Kakaku.com user reviews: TOTO Apricot F3 (Japanese): https://review.kakaku.com/review/J0000042091/
Checked October 2026.
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