How to Measure Bathroom Sink Drain Size [Quick Steps]

When replacing the sink drain or whole bathroom sink, you have to measure the sink drain size. Securing a bathroom sink drain properly will save you from water spillage. You need to make sure the bathroom sink drain is fitted correctly to the plumbing system.

Bathroom sinks vary in design and size. For instance, the undemount sinks, vessel sinks, pedestal sinks, vanity sinks, wall-mounted sinks, console sinks, self-rimming sinks, etc. Each of these designs also has its respective drain size.

Taking the right measurement of a bathroom sink drain size is crucial so that you may get the right size bathroom sink drain that fits properly.

This guide has been put together to help you handle this task without a plumber’s assistance and extra cost.

Bathroom Sink Drain Size Measuring

How to Measure Bathroom Sink Drain Size:

You will need some tools to measure the bathroom sink drain pipe diameter, which is equivalent to the sink drain size.

  • Adjustable wrench
  • Plumbing measuring tape or ruler
  • Pliers
  • Lubricant

The holes within the sink drain of bathroom sinks are usually small to prevent clogs or blockages. Its standard size is 1.25 inches. Other common sizes for drain openings are 1.5 and 1.625 inches.

Their job is to pass the water from the sink basin to the drainpipe. The drainpipe then leads to the drainage system, effectively getting rid of wastewater.

Step 1. Detach the sink drain pipe

You should begin by removing the pipe connected to the sink drain if it is already attached. You will get more accurate measurements by doing so.

Next, apply the lubricant to make it easy to remove, and use the adjustable wrench to detach the drain pipe from the drain hole outlet. This also helps you drain the water that the sink drain may be retaining.

Step 2. Hold the sink drain in place

Using the large adjustable wrench, hold the sink drain steady. Keeping the sink drain stable is crucial to getting accurate results.

Step 3. Measure the drain opening size

Measure the sink drain hole opening with the measuring tape. You will get the diameter of the drain pipe. Then, using a ruler, measure the bottom end of the drain.

Do this by inserting the ruler into the sink and taking the measurement from the straight edge. Write down the measurements so that you can remember them.

The steps listed above are explicitly explained to guide you through measuring your bathroom sink’s drain. Other important factors to consider include the sink position and material.

For sinks above the countertop, their drains should have a mounting ring. A mounting ring provides the sink with the needed support that a cabinet would give instead.

Bathroom Sink Drain Sizes

The only function of a bathroom drain sink is to drain away from the sink. Sink drain sizes are nowadays standardized to achieve this and make switching drains easier. Various kinds of drains in different rooms of the home have varying sizes.

A bathroom sink drain is smaller than a kitchen sink drain. There is little need for a large drain hole because we only use it to wash hands, brush our teeth and shave.

Although some bathroom sinks may have drains pipes that connect to a one and a 1/4-inch tailpiece, most contemporary bathroom sink drains have a one and a 1/2-inch outlet.

All of the pipes that connect to the rear piece, along with the P-trap assembly and all lateral extensions, have a diameter of 1 1/4 or 1 1/2 inches. Wider drain pipes are recommended because they allow for a faster flow of water.

You can use an adapter to swap from a narrow drain pipe to a wider pipe amid the system.


Bathroom sink is a vital part of any bathroom. It is, therefore, important that its components are installed appropriately. Wrong installations can cause leakages that can ruin your sink cabinet or, even worse, your bathroom.

The information in this guide will help you measure a bathroom sink drain. This guide has been carefully put together to help you select the right drain size for functionality and style.

Lisa Burks

Hi, I'm Lisa Burks, founder of the Sink Formula blog, and plumber of 5 years experience.

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