How To Measure Undermount Kitchen Sink

Not only are undermount kitchen sinks attractive and minimalistic, but they are also quite functional in their design. Because they don’t have exposed rims, they don’t catch crumbs and dirt which makes cleaning easy. But before you can get to use your undermount kitchen sink and enjoy it, you need to install it first.

Perhaps the very first step to installing an undermount sink is taking measurements. Not only must you know the right things to measure, but also know how to measure undermount kitchen sink. This way you won’t end up with a hole in your countertop bigger or smaller than the sink you have purchased.

Before you begin measurement, ensure your sink is in a stable position by placing it on a flat and stable surface. This can be a sturdy flat table or a stable workbench. Then you need to get basic measuring materials. These include:

  • Measuring tape
  • A straightedge ruler
  • Pen and paper for noting your measurements
With these instruments, you can proceed to take measurements of the length, width, and rim of the sink.

How to measure the length of the sink?

To take measurements you can take a convenient position directly in front of the sink like you were washing dishes. Then place on the end of the measuring tape on the one edge of the sink. Ensure that the tape gets to the outside rim of the sink on that side. From here, stretch the tape to the other edge of the sink. Write down this measurement.

How to measure the width of the rim? 

Standing in the same position you can measure how wide the sink is from the back to the front. Place the tap on end of the tape on the outside rim at the back of the sink. From here measure forward towards you. Note this measurement also and write it down.

Measuring the lip/rim

The “lip” of the sink refers to space in between the countertop edge and the edge sink edge. In most kitchen sinks this is usually not more than 1 inch in length.  For an undermount, it is important that you measure the width of this rim. It should be relatively the same for all four sides and variations less than 1/8 inches are insignificant. Note down this measurement as well.

Measuring and cutting out the hole

With these measurements, you can proceed to cut a hole in the countertop where you want to place the sink. To do this there is a need for some calculations. First, add the measurement of the sink lips for the left and right side. Subtract this from the length measurement you took earlier.

Repeat this same process for the width of the sink. Subtract the rim measurement for the front and back ends from the total width. This will give you the length and width of the hole you will cut. The lips of the sink will sit on top of the countertop on all four sides of the sink.

 While taking your measurement, close attention to the corner radius of the sink and hole you are about to cutout. While there is no need for an accurate calculation of this radius you should still be mindful of it. This way you don’t end up with gaps in your installation.

Do we have a standard size of an undermount kitchen sink?

Yes, on average, most cabinets measure about twenty-four inches deep by thirty-six to forty-two inches high and twenty-five and a half to twenty-six inches wide.

These cabinets can accommodate a standard twenty-two by thirty-three-inch size sink. If you happen to purchase a sink with a larger base, then you may require to expand it a little to create the extra room for the same.

There are also standard sizes for the larger sinks, and hence you should build the cabinet bearing in mind the size of the one that you need to install.

How do I measure the drain of the undermount kitchen sink?

All the manufacturers of the sink drains have come up with a standard size of three and a half inches in diameter. You obtain this measurement when you do it through the center of the drain, from one side to another.

All the other components of the kitchen undermount sink drain, such as the sink strainer, the bowl-shaped piece that is inside the mouth, also match these dimensions. It is rare to find a mismatch in the three components of the sink drain.

What size of the waste pipe can an undermount kitchen sink accommodate?

There are a few types of waste pipes for this purpose. An overflow pipe can be twenty-one and a half millimeters wide. Such waste pipes begin from the cistern, then condenses drains from the boilers.

If the undermount basin is large, then you will also need a large drain pipe. I would recommend a thirty-two-millimeter wide waste pipe. The largest sink can accommodate a waste pipe of up to forty millimeters wide.

Such types are mostly for use in large installations such as the washing machine and food waste disposal units in factories and homes.

Are undermount kitchen sink drains universal?

Just as the sinks are universal, so are the sink drains. In most cases, they measure three and a half inches wide. It does not apply to the undermount sinks alone, but it is also similar to the other types of sinks.

The drains are also available in a wide variety of finishes. That means you can easily match one with your kitchen fixtures such as the sink cabinets pulls and the faucets. It is, therefore, rare to find one that does not fit your appliances in the kitchen.

Why should we measure the width of the rim?

It is to know how wide it will be from the back to the front, and this will help a lot when doing the installation. Another reason is that you should get the correct measurement so that you would be able to match it with other appliances such as the drain and the waste pipe.


Note that this procedure assumes that you have bought a sink and you are cutting a new hole for installation. If it is the other way round and you are replacing an old sink, then measuring the hole first is advisable. Either way, it is important to know how to measure undermount kitchen sink in order to pick one that fits perfectly.

24 thoughts on “How To Measure Undermount Kitchen Sink”

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