Measuring an Undermount Bathroom Sink [Quick Steps]

An undermount bathroom sink is an essential part of your bathroom. When replacing the existing sink, it’s necessary to know the right undermount bathroom sink size. To get your old bathroom sink correct size, you need to measure it.

You may wonder how to measure an undermount bathroom sink. The procedure involves simple steps to follow. It’s not possible to fix an undermount sink with measurements different from the sink-cut-hole or previous sink. Also, you don’t have to measure the entire sink. To get the right sink size, the places to measure are the height, width, and depth.

When you perform the process correctly, you will acquire the proper measurement with the first attempt. Fortunately, the process is quick and easy, as demonstrated in this guide.

How to Measure an Undermount Bathroom Sink

5 Steps of Measuring an Undermount Bathroom Sink:

Step 1: Collect the Required Items

You need some items to help you with the process. Otherwise, you will not get the correct size for your undermount sink. They include the following;

  • Pencil
  • Paper
  • Tape measure
  • Clean rag

Step 2: Clear and Clean the Sink

Since the sink has been in use, it could be dirty and wet. You will have to remove any stuff on its surface and clean it. Then dry it using a clean rag. Otherwise, the mess can affect the measurements.

Step 3: Measure the Sink’s Width

When the sink is ready for measuring, start with the width. The sink’s width entails its wideness. You will measure how wide the sink is from one end, all the way to the other. Use a tape measure and record your findings on paper.

Most undermount bathroom sinks come with a standard width of 22 – inches.

Step 4: Measure the Sink’s Depth

After recording down the measurements of the width, proceed to measure the depth. Unfortunately, most people confuse the sink’s height with its depth. 

An undermount bathroom sink’s depth is the distance from its front to the back. Place your tape measure on the sink’s end, near the faucet, and the other end, which’s near you. Then read the measurements and record them.

Step 5: Measure the Sink’s Height

With the width and depth measurements, you only need the height size to know the sink size to replace. The height entails your sink’s deepness. Start measuring using a tape measure from the place the sink meets the countertop to its deepest part.

Record what you find on a piece of paper.

You should be careful while taking the height measurements as the sink may not fit if you pick a shorter or taller sink than the previous one.

After getting the sink’s height measurement, you will have successfully measured your undermount bathroom sink. The next step is to use all the above measurements to buy your replacement sink.

The above information indicates that it’s like a downhill task to measure an undermount bathroom sink. Some sinks are small, standard, while others are pretty big, like the double basin sinks. The process of measuring them all is the same.

But most bathrooms use standard undermount sinks. That’s why it’s essential to have the following knowledge about them;

Standard Undermount Bathroom Sink Size

Undermount bathroom sinks are of different shapes. If round or vessel, the sink’s diameter should be between 16 – 20 inches. The average water depth should be approximately 5 – 8 – niches.

As for the standard-sized rectangular undermount bathroom sinks, the side-to-side sizes should lie between 19 to 24 – inches. Their front-to-back distance should be approximately 16 – 23 – inches. Their water depth should be around 5 – 8 –inches.

If your bathroom is ADA compliant, the typical undermount bathroom sink should have a width of 30 – inches and be approximately 11 – 25 – inches deep.

If you are fixing a standard undermount sink in your bathroom, ensure it corresponds to what you will use it for. Remember buying and installing a sink is a long-time investment venture. You wouldn’t want to do it today then have it redone soon. It will be a waste of money and time.

A bathroom used by an average number of people is ideal for installing a typical standard-size undermount sink. Such a sink is also excellent to use for everyday morning rituals and bathroom needs.

Fix a small sink if you are the only one to use it or if you need it for washing hands only.

A bathroom for many people requires large undermount sinks. You can bathe your child or fury pal in such sinks, wash your hair, or perform some laundry cleaning.

A standard rectangular undermount bathroom sink should contain bowl dimensions ranging from 1 ½ – 2 ½ – inches. These measurements aren’t limited to the numbers given. They offer you direction when choosing a standard undermount sink for your bathroom.

The only essential thing to consider about the size of a typical undermount sink is its width and depth. The two should not exceed 30 – inches and 22 – inches, respectively.


Knowing your undermount bathroom sink size before installing is essential. It will save you from various inconveniences like reordering a new sink. Some sink stores don’t accept already sold items. In such a case, you will have to buy another sink if what you purchased does not fit.

Undermount sinks are usually attractive and improve the look of a bathroom. Fixing a smaller or larger sink than required may make the sink and space look awful. They may also not function properly. The best solution is to measure the size of the undermount sink you want to install in your bathroom.

When you do it correctly, you will get the exact sink size you require. Luckily, the procedure is quick and easy, as demonstrated above.

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