Installing an Undermount Sink requires precise measurements to ensure a perfect fit beneath the countertop. Unlike drop-in models, undermount sinks sit below the counter surface, creating a seamless and modern look. Measuring accurately helps prevent leaks, alignment issues, and countertop damage. This guide explains how to measure an undermount sink step by step, along with expert tips for selecting the right model for your kitchen or bathroom.

Understanding the Structure of an Undermount Sink

An undermount sink is mounted under the countertop, meaning the rim of the sink is not visible from above. It provides a smooth transition from counter to basin, making cleaning easier and improving aesthetics. The sink attaches directly to the underside of materials such as quartz, granite, or solid surface counters. To achieve a proper fit, the measurements must match both the sink and the cutout on the countertop.

Step 1: Measure the Cabinet Size

Start by measuring the interior width and depth of the sink base cabinet. This determines the maximum sink size your cabinet can accommodate.

Ensure there’s at least 2 inches of clearance between the sink and cabinet walls for mounting clips and plumbing connections.

Step 2: Measure the Countertop Cutout

The cutout in the countertop must match the sink dimensions. If replacing an existing sink, measure the old cutout from below using a flexible measuring tape.

1. Measure the length from left to right across the cutout.

2. Measure the width from front to back.

3. Record the corner radius if applicable (some sinks have rounded corners).

4. Add or subtract a few millimeters if your new sink has different rim thickness.

For new installations, use the manufacturer’s cutout template. Most professional sink brands, such as LANSIDA, provide precise CAD drawings or paper templates to simplify this process and ensure alignment with the countertop edge.

Step 3: Measure the Sink Bowl Dimensions

Measure the outer and inner dimensions of the sink itself to verify that it matches your cabinet and countertop space.

• Overall Length and Width: Measure from one outer edge to the other at the widest points.

• Bowl Depth: Measure vertically from the rim to the bottom of the basin.

• Divider Height (for double bowls): Measure the center partition to confirm drainage alignment.

• Flange Thickness: For undermount sinks, note the thickness of the rim, usually 1.2–1.5 mm for stainless steel models.

When choosing a model like LANSIDA’s stainless steel undermount sinks, pay attention to corner radius and bowl depth, as these affect how much usable space you have and how the sink aligns under the countertop.

Step 4: Measure Faucet and Accessory Spacing

Since undermount sinks do not have deck holes, the faucet, Soap Dispenser, or filtered water tap must be installed on the countertop. Measure the distance between:

• The sink edge and backsplash.

• The faucet hole centerline and sink centerline.

• Any existing cutouts for accessories.

Allow at least 2 inches behind the sink for faucet clearance. If you’re planning to install accessories such as a colander, drain grid, or cutting board, check the interior bowl width for compatibility.

Step 5: Confirm Installation Depth and Clearance

Accurate depth measurement ensures proper drainage and alignment with plumbing fixtures. To calculate the required space:

1. Add the sink bowl depth and countertop thickness.

2. Subtract this total from the available height inside the cabinet.

3. Ensure at least 1 inch clearance above the plumbing trap.

This calculation helps prevent interference with garbage disposers or under-sink filtration systems. LANSIDA’s undermount sinks are designed with optimized bowl depths that balance capacity and installation flexibility, making them suitable for both compact and full-sized kitchens.

Step 6: Account for Overhang and Reveal Style

There are three types of reveals when mounting undermount sinks:

• Positive Reveal: Countertop edge sits slightly inside the sink, exposing a small rim.

• Zero Reveal: Countertop and sink edges are flush.

• Negative Reveal: Countertop overhangs the sink edge for a seamless look.

To achieve your preferred reveal style, measure and mark the countertop cutout carefully. Always check the manufacturer’s installation guide before cutting. LANSIDA provides detailed mounting instructions to help you achieve a professional finish regardless of your chosen reveal style.

Professional Tips for Accurate Measurement

• Always measure twice before making any cuts or orders.

• Use a rigid steel ruler for straight edges and a flexible tape for curved areas.

• Ensure the countertop is level before final measurements.

• Leave space for mounting clips and silicone sealant between the sink and counter.

• Keep a 1/8-inch tolerance for stainless steel sinks to allow for manufacturing variances.

Choosing the Right Undermount Sink

The right sink not only fits your space but also enhances the performance and design of your kitchen. When considering material, stainless steel remains the most popular choice for its durability and easy maintenance. LANSIDA offers a wide range of stainless steel undermount sinks with satin finishes, soundproof pads, and anti-condensation coatings. Their products combine modern design with practical engineering, ensuring long-lasting use and effortless installation.

Conclusion

Measuring an undermount sink requires patience and precision, but with the right tools and steps, you can ensure a perfect fit for your countertop and cabinet. Accurate dimensions help achieve a sleek, gap-free appearance and prevent costly installation errors. For high-quality undermount sinks that provide reliability, aesthetic appeal, and precise engineering, explore the professional collections from LANSIDA. Each sink is crafted with meticulous attention to size compatibility and installation accuracy, ensuring a seamless integration into any modern kitchen.