Sink Cutout Calculator

Estimate the countertop cutout for a kitchen or bath sink and the cabinet width it needs. Enter the sink size and mount type.

edge clearancecutout (dashed)
Cutout Size
in. (L x W)
Opening to cut in the counter.

Usage Tip

Tape the template down, mark it, and dry-fit before cutting. Drill a starter hole inside the waste area for the jigsaw, and on laminate cut from the top with masking tape to limit chipping.

THE MATH
Cutout length = Sink length − allowance
Cutout width = Sink width − allowance
Drop-in allowance ≈ 1″ (rim overlap); undermount ≈ 0 (cut to the bowl)
Drop-in (top-mount) sinks drop into the hole and the rim rests on the counter, so the cutout is a little smaller than the sink. Undermount sinks hang below, so the cutout matches the bowl opening.
The sink base cabinet must be a few inches wider than the sink to fit the bowl and clips.
Always cut to the template supplied with your sink — this is a planning estimate, not a substitute for the manufacturer dimensions.
Keep the cutout at least about 1.5″ from the front edge, back wall, and any seam so the counter stays strong.
Undermount cutouts in stone or solid surface must be smoothed, sealed, and the sink supported from below; drop-in cutouts can be rougher since the rim hides the edge.
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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.