How to Measure for an Undermount Workstation Sink | Template First

Measure a workstation sink by its actual outside dimensions, then set the cutout from that model’s own template — not the nominal sink size.

A sink that looked right on the spec sheet can still fail at the cabinet, because workstation sinks carry accessory ledges, deeper bowls, and rear projections that standard undermounts don’t. The measurement that decides the job happens in four places: the cabinet interior, the sink’s outside edges, the countertop cutout dictated by the manufacturer’s template, and the clearance around the faucet and accessories. Get those four right and fabrication goes smoothly. Skip one and you’re cutting a second hole in a countertop you can’t un-cut.

Start With The Exact Sink Model, Not The Cabinet

Pull the model-specific undermount cutout file, template, and installation instructions before you touch a tape measure. Workstation sinks are not interchangeable — BLANCO’s PRECIS line alone spans a 24-inch minimum cabinet model and a 36-inch minimum model, and those figures apply only to the sinks they’re printed next to.

Confirm three things on the specification sheet:

• The sink is rated for undermount installation (workstation sinks also come in drop-in and farmhouse mounts).
• The minimum cabinet size the maker lists for that model number.
• The cutoff date and version of the template — BLANCO’s own templates carry a warning that they’re approximate guides.

BLANCO’s install guidance is blunt on this point: the physical sink should be on site and compared against the template before any cutting. Order the sink first, cut second.

Measure The Cabinet Interior, Then The Sink Itself

Measure the base cabinet’s clear inside width — the distance between the inner faces of the side walls — rather than the advertised cabinet size. Then account for what’s already in there: drawer boxes, pull-outs, structural supports, plumbing, and the space below the countertop that clips or support blocks will occupy. A drawer box that fouls the sink’s rear ledge is the most common surprise on a retrofit.

Next, measure the sink at its widest points, including any rim or mounting flange. Record length, width, bowl depth, drain location, accessory ledge height, and every rear or side projection. For reference, a BLANCO PRECIS model lists a 19.75 × 15.75-inch bowl interior with a 7.5-inch depth; another lists a 17 × 16-inch bowl with a 9.5-inch depth. Bowl dimensions are not outside dimensions, and the cutout is keyed to the outside.

Set The Cutout From The Template And The Reveal

The countertop opening follows the model’s template plus whichever reveal you choose, and the reveal must be settled before fabrication begins. BLANCO describes three options: a positive or partial reveal that leaves some sink rim visible, a zero reveal that sits approximately flush with the bowl edge, and a negative reveal where the counter overhangs and hides the rim.

Reveal figures differ by template — BLANCO’s general undermount guidance cites 1/8 inch for most templates, while a Diamond template specifies 1/4 inch. The template in hand always wins over the general rule. One BLANCO template example lists an outside size of 22 7/16 × 20 5/32 inches and states plainly that the template is approximate.

Before cutting, tape the template down, confirm its orientation and model name, and drill a pilot hole. Check that the opening leaves enough countertop material around the sink and that all faucet, soap dispenser, and filtered-water holes fall on solid surface. If you’re still deciding which model fits your kitchen, our tested undermount workstation sink roundup compares real cabinet requirements side by side.

Two more checks BLANCO’s documentation flags: an undermount sink needs a strong, sturdy countertop material, and the exposed cut edge must be finished rather than left rough. Ask your fabricator what they require for material, thickness, edge finish, and fastening.

Where Most Measurements Go Wrong

Almost every failed undermount cut traces back to one of a short list of shortcuts. BLANCO’s installation and template documents name them directly, and each one is cheap to avoid and expensive to fix.

• Cutting from the sink’s nominal size instead of measured outside dimensions.
• Using a generic template rather than the exact model’s undermount file.
• Choosing the reveal after the countertop is already cut.
• Ignoring drawer boxes, partitions, supports, faucet holes, or accessory clearance.
• Assuming a workstation sink fits a standard base cabinet.
• Cutting before verifying template orientation and model number.
• Leaving the countertop cut edge unfinished.
• Overtightening mounting clips, or mounting to an unsupported counter.
• Installing a sink that arrived damaged — inspect it first, and treat the edge as sharp.
• On a replacement job, checking only the existing countertop opening and not whether the new sink fits inside the cabinet.

Plan the faucet, strainer, and accessories before the sink goes in; BLANCO’s instructions call for installing those components first, then tightening clips in sequence without overtightening. When the sink is seated and the clips are snug, the rim sits inside the cutout with the reveal you chose showing evenly at the front edge.