Most people go their entire adult lives not realizing toilets come in two shapes UNTIL they buy the wrong seat. Super fun way to spend a Sunday. If you’ve broken your existing toilet seat, are tired of pooping on a wobbly seat, or are considering upgrading to a bidet, spend 2 minutes learning how to measure a toilet seat to avoid booty disappointment!

How to Measure A Toilet Seat
Step 1: Grab a Tape Measure
Step 2: Measure the Seat Length/Width
Step 3: Measure the Bolt Spread

1. Identify Your Toilet Shape

Every standard size toilet seat is one of two shapes: round or elongated. A round toilet bowl looks like a perfect pizza pie shape, while an elongated bowl is longer and more ovular.

If you install the wrong size, you’ll know pretty quick! A round seat on an elongated toilet will expose part of the bowl. And an elongated seat on a round toilet will hang off the bowl edge.

Here’s how to  do some simple toilet seat measurements to get the right size the first time. 

2. Gather Your Tools

You will need:
• A measuring tape
• Pen and paper or your phone notes app
• A screwdriver/wrench to remove your old seat 

• All-purpose cleaner to give your throne a shine

3. Measure the Seat Length

Remove your existing toilet seat. You may need to unscrew the seat or simply pop it off if it’s a quick release design.

Measure from the center of your bolt spread (where the seat fastens to the toilet) to the outside front edge of the toilet bowl. 

If your toilet bowl is ~16 ½ inches long, it is rounded.
If your toilet bowl is ~18 ½ inches long, it is elongated. 

If your toilet length is shorter or longer, you may have a custom or specialty toilet. (Are you famous?) Keep reading to learn how to measure the rest of your toilet so you can assault Home Depot with questions.

4. Measure the Seat Width

Measure from the widest point of your toilet from lip to lip. A standard toilet bowl should measure around 14 ½ inches, but there are some slight variations between brands. Write down the exact width to include in your online search or to bring with you to the hardware store. 

5. Measure the Bolt Spread

Your bolt spread is likely to be 5 ½ inches if you’re rocking a US standard toilet. Measure from the center of the left bolt hole to the center of the right bole hole to be sure!

*Sorry for saying bolt hole. 

Measuring Your Toilet Seat for a Bidet

Most modern bidet attachments adjust to fit the majority of standard toilets. It’s important to check the specifications of the bidet attachment you’re considering to ensure the bidet control panel will fit between your toilet and the wall. You should also measure the distance from the middle of the boltholes to the tank to ensure you have sufficient clearance.

If you are upgrading to an electric bidet seat, you will need to choose between a round or elongated bidet seat and should follow the length measurement guides below:

~16 ½ inches long (420mm) = rounded bidet seat.
~18 ½ inches long (470mm) = elongated bidet seat.

Toilet seat size isn’t the only factor you need to consider when installing a bidet. You might have a skirted toilet (smooth surface at the base) or a flushometer (a tankless toilet) which may require special adaptors and additional connections. It’s always a good idea to check your toilet compatibility before purchasing or chat with a customer service expert.

Knowing how to measure a toilet seat isn’t the sexiest life hack. But it will save you from multiple trips to the hardware store and ensure you order the right attachments for your toilet. Time is precious and so is pooping without pinching your bum in a cracked seat. 

Frequently Asked Questions

What are the standard toilet sizes?

Standard US toilets typically measure 14 ½ inches wide x 16 ½ inches long for a ROUNDED toilet seat or 14 ½ inches wide x 18 ½ inches long for an ELONGATED toilet seat. 

What is the difference between elongated and round toilet seats?

Rounded seats will appear more circular with a shorter length, while elongated toilet seats are longer and more ovular. Both sizes should have the same width.

How do I know my toilet seat size?

Simply remove your toilet seat and measure your toilet bowl. Use a tape measure to determine the length (from the middle of the boltholes to the outer front edge of the bowl) and width (measuring the seat at the widest point lip to lip).