Sink Cutout Calculator

Calculator Inputs

Example Data Table

Examples are approximate and depend on your exact inputs.

Formula Used

• Adjusted dimensions: L′ = L + 2m, W′ = W + 2m, where m is the margin.
• Rectangle area: A = L′ × W′
• Rectangle perimeter: P = 2(L′ + W′)
• Rounded rectangle area: A = L′W′ − (4 − π)r′²
• Rounded rectangle perimeter: P = 2(L′ + W′ − 4r′) + 2πr′
• Circle: A = πr², P = 2πr, with r = (D + 2m)/2
• Oval (ellipse) area: A = πab, with a = (A + 2m)/2 and b = (B + 2m)/2
• Oval perimeter: Ramanujan approximation using a and b.
• Kerf loss area (estimate): A_kerf ≈ P × k, where k is kerf width.
• Waste factor: Apply multiplier (1 + w/100) to area and perimeter-based sealant.
• Clip estimate: clips = ceil(P / s), where s is clip spacing.

How to Use This Calculator

1. Select your working units to match your tape and template.
2. Choose the cutout shape that matches the sink’s template.
3. Enter dimensions from the template, not the sink rim.
4. Add a margin if you need extra clearance or a tighter fit.
5. Enter corner radius for rounded templates and jigsaw routing.
6. Set kerf width to estimate material removed during cutting.
7. Choose a waste factor for sealant and rework allowances.
8. Click Calculate to view results above the form.
9. Download CSV or PDF to attach with your job paperwork.

Professional Field Notes

1) Why cutout accuracy matters

Countertop cutouts control how the sink seats, how clips engage, and how sealant performs. A small oversize can reduce clip bite and invite movement; a tight cutout can chip laminate, quartz, or stone during test fitting. Many installers aim for a consistent clearance that matches the template’s guidance, then verify with a dry fit before final sealant.

2) Typical clearances and margins

For drop-in sinks, clearances are often modest because the rim hides the edge, while undermount installs demand cleaner edges and more controlled tolerances. Common template offsets range around 1/16–1/8 inch (about 1.6–3.2 mm) depending on sink style, countertop material, and edge finishing. This calculator’s margin parameter lets you model both looser and tighter fits.

3) Choosing the right shape model

Rectangles suit many steel and composite sinks. Rounded rectangles better represent routed corners where a jigsaw cannot produce sharp inside corners. Circles are used for bar sinks and specialty basins. Ovals approximate elliptical bowls and some farmhouse prep sinks. Selecting the closest shape improves perimeter and sealant estimates, not just area.

4) Corner radius and tool reality

Inside corner radius is dictated by your method: a jigsaw often leaves a larger inside radius than a router with a small bit. If the template radius is smaller than your tool can achieve, you may need corner relief or a router pass. The rounded-rectangle formula accounts for curved corners and limits radius to half the smaller side.

5) Kerf and material removal

Blade kerf is the width of material removed; a typical jigsaw blade can be around 0.04–0.06 inch (1.0–1.5 mm), while some blades are wider. The kerf loss area estimate uses perimeter multiplied by kerf width. It does not replace careful layout, but it helps explain why “perfect” lines still remove measurable material.

6) Waste factor for real jobs

Waste covers layout errors, chipping allowances, extra sealant, and rework. Many crews carry an 5–12% planning factor for small fabrication tasks, increasing it for brittle finishes, large spans, or rushed schedules. Here, waste scales both cutout area (planning) and sealant length (consumables), so your paperwork matches field reality.

7) Sealant planning and bead control

Perimeter directly drives bead length. Add extra for inside corners, overlaps at start/stop points, and cleanup. If you typically run two beads (one under rim, one at edge), multiply the sealant length accordingly. Accurate perimeter also helps estimate masking tape length and clamp/clip staging time.

8) Clip spacing and support strategy

Support clips vary by sink and countertop system. Spacing around 10–14 inches (250–350 mm) is a common planning range, with closer spacing near corners or high-load areas. This calculator estimates clip count from perimeter and spacing so you can pre-stage hardware, reduce interruptions, and keep installation consistent.

FAQs

1) Should I measure the sink or the template?

Measure the manufacturer template whenever possible. Templates already include intended clearances and corner radii, and they reduce interpretation errors compared with measuring the sink body or rim.

2) What margin value should I start with?

Start with the template’s recommended offset. If you must choose, many jobs use about 1/16–1/8 inch (1.6–3.2 mm), then refine after a dry fit and edge finishing plan.

3) Why is rounded rectangle better than rectangle?

Most tools cannot cut perfectly sharp inside corners. Rounded rectangle models curved corners, producing more realistic perimeter and sealant estimates when the template includes corner radii.

4) How accurate is the oval perimeter?

The calculator uses a respected approximation that is very close for common proportions. For extremely elongated ovals, verify perimeter with a physical template trace if sealant budgeting is critical.

5) Does kerf change my final cutout size?

Kerf removes material, so cutting on the wrong side of your line can oversize the opening. The kerf estimate helps you plan, but layout and steady tool control determine the final result.

6) Do I apply waste to area only or also sealant?

Both can benefit. Area waste supports planning and rework, while sealant waste accounts for overlap, starts/stops, cleanup, and occasional bead redo, especially on textured or dusty surfaces.

7) My clip count seems high. What should I check?

Review your spacing input and units, then confirm your sink’s recommended clip layout. Some systems use fewer clips plus adhesive; others require more clips for heavy basins and undermount installs.

Measure carefully, cut once, and install with confidence today.