🔧 Countertop Cutout Calculator
Enter your sink's outer dimensions and mount type to get the countertop cutout size, corner radius, and front setback — for a drop-in with a rim lip or an undermount with a reveal.
🔧 Sink & Mount
What is a Countertop Cutout Calculator?
It turns a sink's outer size and mount type into the opening to mark on a countertop. For a drop-in sink it subtracts the rim lip on each side so the rim rests on the counter; for an undermount it subtracts the reveal on each side so the counter overhangs the bowl. It also returns a corner radius and a front setback for a safe, strong cut.
Use it to check a sink will fit your countertop and cabinet, to plan a cutout before you order stone, or to understand the difference between drop-in and undermount openings. It's a planning aid — always trace the template that ships with your sink before you cut.
❓ Frequently Asked Questions
How big should a sink cutout be compared to the sink?
It depends on the mount. For a drop-in sink the cutout is smaller than the sink's outer dimensions by the rim lip on each side, so the rim can rest on the counter — this tool defaults to a 0.5-inch lip. For an undermount sink the cutout is smaller than the bowl opening by the reveal on each side, so the countertop overhangs the bowl slightly — the default reveal is 0.125 inch.
What is the reveal on an undermount sink?
The reveal is the strip of countertop edge that shows above the bowl rim when you look down at an undermount sink. A positive reveal means the counter overhangs the bowl by that amount all around, so the cutout is smaller than the bowl opening. A zero reveal lines the cutout up flush with the bowl, and a negative reveal exposes the bowl lip — this calculator uses a small positive reveal by default.
Why does the cutout need a corner radius and a front setback?
A rounded corner — about 1.5 inches by default — is easier and safer to cut in stone or solid surface than a sharp inside corner, which can crack under stress. The front setback is how far the cutout sits back from the front edge of the countertop, typically around 1.5 inches, to leave enough material for strength and a comfortable working lip.
Should I still use the sink's paper template?
Yes — always. This calculator gives you planning dimensions to confirm the sink fits your countertop and cabinet, but the paper or cardboard template supplied with the sink is what you should trace before cutting. It captures the exact bowl shape, corner radii, and mounting-hole positions for your specific model, which a length-and-width estimate cannot.