Written by: Deane Biermeier / Facts Checked by; Ryan Cullenward / Products Tested by Licensed Interior Designers
Choosing the right size toilet seat is crucial for both comfort and functionality in your bathroom. Whether you're replacing a worn-out seat or upgrading for improved aesthetics, knowing exactly what size you need can save time, money, and frustration. In this comprehensive guide, we will walk you through how to determine the correct toilet seat size, what types are available, and how to ensure the perfect fit.
Before taking measurements, it’s important to understand the two standard toilet seat sizes found in most homes:
Length: Approximately 16.5 inches from the mounting holes to the front edge.
Shape: Nearly circular.
Common in older homes or where space is limited.
Ideal for small bathrooms due to their compact footprint.
Length: Approximately 18.5 inches from the mounting holes to the front edge.
Shape: Oval or egg-shaped.
More common in newer homes or commercial buildings.
Preferred for comfort, especially for adults and larger users.
To determine the correct toilet seat size, you’ll need to take three precise measurements. All you need is a tape measure or ruler and a few minutes of time.
Place the tape at the center point between the two seat bolt holes at the back of the toilet.
Measure straight forward to the outer front edge of the bowl.
If the length is around 16.5 inches, your toilet requires a round seat.
If the length is around 18.5 inches, you need an elongated seat.
Measure the widest point across the bowl.
Most toilet bowls, regardless of being round or elongated, will measure around 14 to 14.5 inches in width.
Measure the distance between the two bolt holes at the back of the toilet bowl.
The standard spread in the U.S. is 5.5 inches, but it’s good to verify, especially for European or specialty models.
Some toilets may have non-standard shapes or come from international manufacturers with different sizing conventions. Be sure to:
Identify the brand and model of your toilet (often stamped inside the tank).
Check for specialty shapes like D-shaped, square, or compact elongated.
For wall-mounted toilets, measurements and fitting may vary significantly.
While size is the primary concern, choosing the right material ensures longevity and comfort.
Lightweight and inexpensive
Available in a variety of shapes and colors
May feel cold in colder climates
Offer warmth and classic aesthetic
More durable and solid feeling
Often slightly more expensive
Eliminate loud slamming
Ideal for families with children
Available in both round and elongated designs
1. Check your existing seat: Many have model numbers underneath or sizing details.
2. Use a sizing template: Some manufacturers provide printable guides.
3. Bring your measurements when shopping online or at a hardware store.
4. Take a photo of your toilet bowl next to a ruler or tape for easy comparison.
Some toilet manufacturers, like Kohler, Toto, or American Standard, may offer proprietary designs. If your toilet bowl doesn’t fit standard round or elongated measurements:
Contact the manufacturer directly for compatible seat models.
Check for universal-fit adjustable seats available online.
Consider replacing with a standard bowl if seat replacements become too difficult to find.
Ideal for elderly or mobility-impaired users
Adds height for easier access
Available in both round and elongated versions
Require electrical outlet for advanced features
Provide extra comfort
May not be as durable over long-term use
Guessing the size without measuring
Assuming all toilets are the same
Forgetting to check bolt spacing
Ignoring specialty shapes
Always double-check measurements and consult the product description before purchase.
You can find toilet seats at:
Home improvement stores like Home Depot or Lowe’s
Online retailers like Amazon, Wayfair, and Walmart
Manufacturer websites for proprietary or specialty seats
Make sure the seat description includes:
Compatibility with round or elongated bowls
Exact dimensions and bolt spacing
Return policy, in case of sizing errors
1. Remove the old seat by unscrewing the bolts at the back.
2. Clean the area thoroughly with disinfectant.
3. Align the new seat’s bolt holes with the toilet’s holes.
4. Tighten the bolts securely but not too tight to avoid cracking.
5. Test the seat for fit and stability.
Most seats come with universal hardware, making replacement straightforward.
Finding the correct toilet seat size is simple when you measure accurately and know your bowl type. By following this guide, you can ensure that your next toilet seat will provide the perfect fit, lasting durability, and ultimate comfort for your needs.
Disclosure: Sanitarysupply.org receives an affiliate commission on some, but not all, of the products we recommend—but only if you decide to click through to the retailer's site and make a purchase.
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