How to Measure a Bathroom Sink | Size Lavatory Sink for Replacement

How to Measure a Bathroom Sink

how to measure a bathroom sink drop-in configuration

If it’s time to replace a bathroom sink, you need to know more than just what size you are looking for before you start shopping around. There are many other considerations to keep in mind, like the depth, what hole configuration you want (which could change if you are planning to update your faucet), and where the new sink will be placed. Here you will learn how to measure a bathroom sink to make a confident purchase. How you measure depends significantly on the type of sink. At PlumbersStock, we categorize our bathroom sinks into four types:

  1. Drop-in sinks
  2. Undermount sinks
  3. Vessel sinks
  4. Pedestal sinks

Measuring a Drop-In Sink

A drop-in (or self-rimming/top mount) sink is one of the most common installations. One reason is that it’s so easy to install. The sink's rim overlaps the edge (cut-out) of the sink hole, accommodating imprecise cuts. The sink will provide cover for imperfections.

Sink Dimensions (Actual Sizes)

  • Sink width is measured from the front outer edge to the back outer edge.
  • Sink length is measured from left outer edge to right outer edge.

Basin Dimensions (Bowl Sizes)

how to measure a bathroom sink wall-mounted
  • Depth* is measured from the bottom of the basin's interior to the top of the rim.
  • Basin height is measured from the basin's underside (lowest point) to the top of the rim.
  • Basin Width is measured from the front inner edge to the back inner edge.
  • Basin Length is measured from left inner edge to right inner edge.

* The depth can be confusing because sometimes sink depth is measured front to back, so pay attention to this detail. Anything with a depth of more than 10" or 11” would be regarding front to back.

The sink width and length measurements should be larger than the sink hole (called a cut-out) by about 3/4” on each side. The same goes for the front and back edges, or around the rim, if it’s circular and not a square. Again, it doesn’t have to be exact because self-rimming sinks are forgiving.

Tips for Measuring an Undermount Sink

You measure an undermount sink the same way you measure a top-mount configuration. However, with an undermount sink, the most critical measurements will be the basin sizes. You will want to ensure that the cut-out will not cover any of the bowl. The ideal undermount situation needs the best water flow from the top of the counter into the Basin. The rim dimensions are about 1-1/2” larger than the sink opening. Each sink will be a bit different depending on manufacturer specifications and weight.

How to Measure a Vessel Sink

Again, you take the measurements the same way, but this time with a special focus on sink height. This is especially important when factoring in the faucet. You have to make sure that the new sink will fit under your faucet with enough clearance to operate a comfortable distance over and away from the rim. If you’ve ever washed your hands in a sink with too little clearance, you will know how irritating it is to continually bump into the faucet spout and basin as you try to wash your hands. Buyer remorse will creep in, especially if you can’t install the setup because clearance is such an issue.

Tips for Measuring a Pedestal Sink

The distinction with pedestal sinks is that you must consider the height of the pedestal (the base). You must first observe the environment in your bathroom. Is the mirror low? Will a taller pedestal and basin conflict with the height of the mirror? Do you have enough room on each side of the basin?

Another thing to consider when measuring a pedestal sink is the location of the supply lines and the drain. A pedestal sink looks and functions best when it is centered on the drain, so make sure that you measure the width of the pedestal in relation to the shutoff valves. And don't forget about the distance from the wall. Is your bathroom big enough to incorporate a larger basin? Even the swing and the size of the bathroom door should be considered.

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