Measure the sink basin first, then the cabinet opening
Start by measuring the sink basin itself — the bowl or bowls where water sits. Measure the length and width at the widest points, from inside edge to inside edge. Write these down. Then measure the depth from the bottom of the basin to the rim. These three measurements tell you what size basin will fit in the space you have.
Next, measure the cabinet opening underneath the sink. This is the hole cut into your countertop where the sink will sit. Measure the length and width of that opening, again from edge to edge. The new sink must fit through this hole. If you are replacing a sink with a different style — say, switching from a drop-in to an undermount — the cabinet opening may need to be enlarged, and that is a separate job.
Take a photo of your current sink from above and from the side. Bring these photos to the store or keep them handy when shopping online. They help you see the style and shape you have now, which matters when you are looking at replacements.
Key Takeaways
- Measure the basin length, width, and depth in inches, from inside edge to inside edge, to know what size will fit in your current space.
- Measure the cabinet opening below the countertop to confirm the new sink will pass through it without modification.
- Note the number of bowls, the faucet hole count and spacing, and whether the sink is drop-in or undermount, because these affect what you can install.
- Bring your measurements and photos to the store, or use them to compare online options against your current sink's footprint.
- If the new sink is a different style than the old one, you may need a plumber to modify the cabinet opening or countertop.
Count the faucet holes and measure their spacing
Look at the back or rim of your sink where the faucet connects. Count how many holes are drilled there. Most sinks have one hole for a single-handle faucet, or three holes for a widespread faucet with separate spout and handles. Some have four or more if they include a sprayer or soap dispenser.
Measure the distance between the holes, center to center, in inches. This spacing is called the faucet spread. A widespread faucet typically has holes spaced 8 inches apart; a single-hole faucet needs only one opening. If you want to keep your current faucet, the new sink must have holes in the same positions. If you are replacing the faucet too, you have more flexibility — but you still need to know what holes the new sink has, so the new faucet will fit.
Check whether the holes are pre-drilled or if the sink comes with a blank rim you can drill yourself. Some replacement sinks let you choose the hole configuration when you order.
Note the sink style and material
Identify whether your current sink is drop-in (sits on top of the countertop with a rim that overhangs the edge) or undermount (attached underneath the counter from below, with no visible rim). This matters because the cabinet opening shape and size differ between the two styles. A drop-in sink can usually fit in a larger opening; an undermount sink needs a precisely sized hole.
Write down the material: stainless steel, porcelain, cast iron, composite, or something else. This is not a measurement, but it helps you find a replacement that matches your kitchen's look and your budget. Stainless steel is common and affordable; porcelain is durable but can chip; cast iron is heavy and long-lasting; composites are newer and come in many colors.
If your sink has a drain hole on one side (single-bowl) or two (double-bowl), note that too. Some people replace a single-bowl with a double-bowl, but that requires a wider cabinet opening.
Measure the rim or mounting surface
For a drop-in sink, measure how far the rim extends beyond the cabinet opening on all four sides. This overhang is usually 1 to 2 inches. The new sink's rim must be at least as wide as the old one, or it will fall through the hole.
For an undermount sink, measure the thickness of your countertop. Undermount sinks are glued and bolted to the underside of the counter, so the counter material and thickness affect how the sink is secured. Granite, quartz, and solid surface counters all work, but the installation method may differ.
If you are unsure whether your sink is drop-in or undermount, look underneath the counter from inside the cabinet. A drop-in sink will have a visible rim or lip resting on the counter edge. An undermount sink will be attached with brackets or adhesive to the underside of the counter, with no rim visible from above.
Check the plumbing connections underneath
Open the cabinet door under the sink and look at the drain and supply lines. Measure the distance from the center of the drain hole in the sink to the wall or the center of the cabinet. This tells you where the drain pipe is located. If the new sink's drain hole is in a different spot, the plumber may need to move the drain line — an extra cost and time.
Look at the hot and cold water supply lines coming in. Note whether they come from the wall, the floor, or the back of the cabinet. If the new sink is a different size or shape, the supply lines may need to be rerouted. Take a photo of the underside so you can show a plumber what you are working with.
If your current sink has a garbage disposal, note its location and size. A new sink with a different bowl configuration may not fit the disposal in the same spot, or you may need a smaller or larger unit.
Bring measurements to the store or use them online
Write all your measurements on a single sheet: basin length, width, and depth; cabinet opening length and width; faucet hole count and spacing; sink style (drop-in or undermount); material; and the location of the drain and supply lines. Take this sheet and your photos to a kitchen or plumbing supply store, or use them to search online.
When you look at replacement sinks, compare the new basin dimensions to your old ones. If the new sink is smaller, it will fit easily. If it is larger, check that the cabinet opening is large enough, or plan to have the opening enlarged. Most big-box stores and online retailers list basin dimensions and faucet hole spacing in their product descriptions.
If you find a sink you like but the faucet holes do not match your current faucet, ask whether the sink comes with blank holes you can drill, or whether you will need to buy a new faucet. Factor that cost into your decision.
Frequently Asked Questions
What if the new sink is smaller than my cabinet opening?
A smaller sink will fit, but there will be a gap between the sink rim and the cabinet edge. For a drop-in sink, you can cover the gap with a trim ring or filler strip. For an undermount sink, the gap is usually hidden underneath the counter, so it is less of a concern. Ask the store whether trim pieces are sold separately.
Can I install a larger sink in the same cabinet opening?
Only if the cabinet opening is large enough. Measure the opening first. If the new sink is wider or longer than the opening, a plumber or contractor will need to enlarge the opening by cutting the countertop and cabinet. This is possible but adds cost and time to the project.
Do I need to replace the faucet if I replace the sink?
Not necessarily. If the new sink has faucet holes in the same positions as the old one, your current faucet will fit. If the holes are in different spots, you can either drill new holes in the sink (if it is not yet installed) or buy a new faucet. Some people use a replacement as a chance to upgrade the faucet anyway.
What is the difference between a drop-in and undermount sink, and does it matter for measurement?
A drop-in sink rests on the countertop with a visible rim; an undermount is attached underneath. Drop-in sinks are easier to install and work in most cabinets. Undermount sinks look cleaner but require a thicker, stronger countertop and professional installation. Measure the cabinet opening and countertop thickness to know which style will work for you.
Should I hire a plumber to measure, or can I do it myself?
You can do the basic measurements yourself with a tape measure. A plumber is helpful if you need to move drain or supply lines, enlarge the cabinet opening, or if you are switching from drop-in to undermount. Get a quote from a plumber before you buy the sink, so you know the full cost.