How to Measure an Undermount Kitchen Sink

Whether you need to measure an undermount kitchen sink for replacement or for first-time installation, getting the right measurements is important. Undermount sinks often require more support than drop-in sinks.

For this reason, estimating the amount of counter space and cabinet space you will need can all depend on how are kitchen sinks measured.

There are several different measurements that are involved when it comes to a sink. The length and width are the main measurements that you will need to understand how much counter space from side to side you will need.

The sink height is the distance between the top lip of the sink and the bottom. This measurement will help determine how high you need to build any support apparatus underneath.

Knowing how to measure undermount kitchen sink units and any necessary accoutrements can play a huge role in your overall kitchen design.

6 Steps to Measure Undermount Kitchen Sink:

An undermount kitchen sink sits flush with the surrounding countertop. The appeal of having an undermount sink is that only the bowl is visible, so your counter top has a smooth, uninterrupted appearance.

Materials you will need:

  • Measuring tape or ruler
  • Pen or pencil
  • Leveling tool
  • Flashlight

Step One: Measure Sink Length

Measuring a undermount stainless steel farmhouse kitchen sink is easy if you start with the length, which is the longest edge of the sink.

Place your measuring tape at the farthest lip of the sink and stretch it to the other end. Be sure that these edges you are measuring are the ones that are farthest away from one another. Write down these figures so you won’t forget them.

Step Two: Measure Width

The width is the shortest edge of the sink.

Place your tape measure or ruler at the back outer edge of the sink. This edge is nearest the faucet and/or handles. Stretch your tape to the front outer edge of the sink. This is the place where you would typically stand when using your sink. Write the number down.

Step Three: Measure Height

The height of a sink is the total area it will occupy vertically. For an undermount sink, this measurement will be from the top of the sink to the underside of the bottom of the sink.

This measurement is very important, especially if you plan on building a support apparatus underneath your sink.

Stretch your measuring tape in a straight line to achieve this measurement, and write down the number.

Note: If you are measuring your sink while it is installed, place your leveling tool on the lip of the sink to ensure a correct measurement. Use your flashlight to get a good look at the underside of the sink while measuring. You can follow same procedure to measure an undermount bathroom sink.

Step Four: Sink Depth

The inner part of the sink, often referred to as the sink bowl, is where depth is measured. Some sinks are angled toward the drain, so it’s always important to notice what the deepest part of your sink interior is.

Place your measuring tape or ruler at that point. Keeping the ruler or tape perpendicular to that surface, measure to where the inner top lip of the sink is. This will be the depth measurement.

Step Five: Distance Between Sink Bottom and Floor

Since an undermount sink does not have support as a drop-in sink has, it’s important to measure the space required to build a support system on which it will rest.

Take your tape measure and place one end at the bottom underside of your sink. Measure from that point to the floor of the cabinet below.

Use your flashlight if you need to get a better look under there. This measurement is crucial, as you will need to know how and where to place your support braces that will hold your sink in place.

Final Step

To understand how your sink compares to other models, you will need to know what is the standard size of a kitchen sink. If your numbers are larger or smaller than the standard size, you will probably need to customize your counter top area to accommodate your sink’s dimensions.

Measuring an Apron Front Kitchen Sink

The unique feature of an apron sink is that its front side is entirely exposed. This front edge should sit flush with the cabinetry below.

Many apron sinks are installed as undermounts. However, they do not require the extra lip of counter top at the front to cover them.

For this reason, apron sinks are considered the feature element of the kitchen instead of the counter top since more of it is visible.

Materials Required:

  • Ruler or tape measure
  • Pencil or pen
  • Pad of paper
  • Leveling tool

Step One: Measure the Front Apron Edge

Apron sinks tend to be much larger compared to what is the standard size of a kitchen sink. Since they will sit on the edge of the cabinetry below and flush with the counter top above, their apron front needs to be measured separately.

Take your ruler or tape measure and place one end at the top lip of the front apron edge. Measure to the bottom of the apron.

Sometimes this will be the total vertical height of the sink, depending on the model. If the bottom of the sink has an unglazed or unfinished appearance, do not include that in the apron measurement.

Step Two: Measure Vertical Height

Now it is time to estimate the total vertical space your sink will require. Evaluate the sink and determine which is the highest point. Sometimes there is an extra lip near the back of the sink, though most apron sinks do not have uneven surfaces.

Measure from the highest point to the bottom underside of the sink. Keep your ruler or tape straight up and down. Use a leveling tool against the bottom of the sink to be sure you have the correct numbers.

Step Three: Measure Bottom Cabinet Area

How are kitchen sinks measured? It depends largely on the type of sink they are, and apron sinks can be special cases. Because the front and top of an apron sink are exposed, there is no way they can support themselves from above.

In other words, unlike drop in sinks, apron sinks will need to sit on something in order to stay in place.

From the bottom underside of your apron sink, measure the distance between the sink and the floor below. Measure the sink’s width, as well.

These measurements will determine how much space you will have to construct a support box on which your sink will sit. Often these structures are made with simple plywood or planks. Though most apron sinks come with mounting hardware that attach them to the counter top above, the extra support will be necessary.

Step Four: Measure the Surrounding Counter Top

Sinks should fit in seamlessly with the counter top that surrounds it like butcher blocks or wood. Each edge should be flush with one another so no leaks or wobbling occurs.

To ensure a snug fit, it’s always a good idea to measure the counter around the sink so you know exactly what you are working with. Take your measuring tape and calculate the width and length of the hole in the counter top.

If your counter top has not been cut, now is a good time to transfer the measurements you have taken for your sink and mark them. It is always better to err on the side of caution. You can always shave away counter top, but it’s much more difficult to put it back if you cut away too much.

Final Step

To be on the safe side, always double-check your calculations. Measure your sink and counter top two or three extra times to make sure you have accurate dimensions.


Measuring an undermount kitchen sink is easy if you know the right steps. Getting accurate numbers is so important, especially if you need to measure a kitchen sink for replacement.

Since sinks of this type are usually heavy and bulky, always take safety precautions. Use a flashlight under the sink so you can get a better look and accurate numbers.

Remember the old carpenter’s advice to measure twice and cut once.

Getting the correct figures can help you avoid having to reconfigure your sink area entirely or making unnecessary adjustments to your counter top. If you measure properly the first time, you can save yourself a lot of hassles when it’s time to install a new sink.

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