A base cabinet is sized by measuring width wall-to-wall, depth from the wall to the front obstruction, and height from the floor to any blocking fixture — always the cabinet body, never the countertop.
Skip the countertop and you get a cabinet that actually fits. Include it, and the new vanity either won’t sit against the wall or won’t clear the door swing.
Bath sink cabinet sizing comes down to three numbers taken in three places. Get those right and the rest — width bands, sink count, plumbing rough-in — falls into line. Get them wrong and you’ll be returning a 48-inch vanity that was never going to clear the toilet.
Here’s the order that works, the standard dimensions to check your numbers against, and the two mistakes that sink most projects.
How To Measure For A Base Cabinet In Three Steps
Measure width wall-to-wall at the cabinet location, depth from the wall to the front obstruction, and height from the floor to the lowest thing overhead. Record them in that order: width × depth × height.
Clear the area first so the tape lies flat. A shampoo bottle or a baseboard can quietly throw a measurement off by an inch.
- Width: run the tape wall to wall at the height the cabinet body will sit. Leave room for side gaps where the walls aren’t square — and in older bathrooms, they rarely are.
- Depth: measure from the wall to the front limit of the cabinet area. Replacing an existing vanity? Measure the cabinet body itself, not how far the countertop sticks out.
- Height: measure floor to the bottom of any window sill, outlet, or obstruction that a taller vanity would hit. Also check that doors and drawers can open without striking the toilet or a side wall.
Then measure the plumbing — drain and supply lines. A rough-in that lands where the new cabinet’s back panel sits will block installation no matter how good your other three numbers are.
Standard Base Cabinet Dimensions To Compare Against
A standard vanity cabinet body is 21 inches deep and 34.5 inches high before the countertop, with widths sold in fixed bands from 24 to 72 inches. Your measured space has to beat those numbers, not match them exactly.
Vanity depth generally runs 18 to 24 inches, with 21 inches as the standard body depth. Base height lands between 32 and 36 inches, with 34 to 36 inches often called comfort height. Add the countertop and the finished surface commonly sits around 36 inches, since countertops add roughly 1 to 1.5 inches of height and front overhang.
| Measurement | Typical Range | What It Decides |
|---|---|---|
| Cabinet body depth | 21 in standard (18–24 in range) | Whether it clears the door swing and walking path |
| Cabinet body height | 34.5 in before countertop | Comfort of use; ~36 in finished with countertop |
| Width | 24, 30, 36, 48, 60, 72 in | Sink count and how much room you have |
| Single-sink widths | 24–36 in | Most bathrooms with one sink |
| Double-sink widths | 48–60 in and up | Shared bathrooms, primary suites |
| Countertop addition | About 1–1.5 in | Finished height and depth beyond the body |
| Front clearance | Doors and drawers fully open | Whether the vanity is actually usable |
Home Depot’s guide to measuring for a bathroom vanity notes that sink count drives width more than anything else — a 24-to-36-inch cabinet suits one sink, while 48 inches and up is where double-sink layouts live. Home Depot’s vanity measuring walkthrough frames depth and width as the two measurements that most often decide the purchase.
Where Most Measurements Go Wrong
Two mistakes account for most failed vanity installs: measuring the countertop instead of the cabinet body, and ignoring side-wall and front clearance.
The first one overstates your usable space. A countertop can add an inch and a half of depth and overhang that the cabinet body doesn’t have, so a replacement vanity measured off the old countertop arrives too deep for the same spot.
The second makes a correctly sized vanity unusable. A cabinet can hit its exact nominal width and still fail because the drawer front smacks the toilet or the door won’t clear a side wall. Measure the front walking space, not just the wall-to-wall span.
The guidance above covers freestanding and base-cabinet vanities in US residential remodels. Floating cabinets and vessel-sink setups need their own height and depth planning, since the sink bowl sits above the counter rather than in it. For a bathroom with tight clearances, a smaller 24-inch vanity with a modern basin is often the more practical buy; our tested bath sink cabinet picks cover sizes from compact singles to double-sink units.
Writing Down Your Three Numbers
With width, above all, your measurements only mean something once they’re on paper. Write down width wall-to-wall, depth from the wall to the front obstruction, and height from the floor to the lowest thing overhead — in that order. Then note your plumbing locations, the cabinet body depth of any unit you’re considering, and how much room its doors and drawers need to open. The standard 21-inch body depth and 34.5-inch body height give you a baseline to test each candidate against. If your measured depth can’t clear 21 inches plus countertop overhang, drop to a shallower vanity or rethink the layout before you order. A five-minute tape measure session now beats a freight return later.
FAQs
What is the standard depth of a bathroom vanity base?
A standard vanity cabinet body is 21 inches deep, with the broader range running 18 to 24 inches depending on the model. That figure measures the cabinet body alone. Countertops typically add about 1 to 1.5 inches of overhang and finished depth, so a vanity measured at the countertop will read deeper than the cabinet you actually bought.
How high should a bathroom vanity cabinet be?
The cabinet body commonly stands 34.5 inches before the countertop, giving a finished surface around 36 inches. Base heights generally fall between 32 and 36 inches, and 34 to 36 inches is often called comfort height. Measure from your floor to any window sill, outlet, or obstruction first — a taller vanity that blocks a fixture won’t work regardless of the standard.
What width vanity do I need for two sinks?
Double-sink vanities generally start at 48 inches wide and run through 60 and 72 inches. Single-sink cabinets most often come in 24, 30, and 36 inches. The deciding factor is your measured wall-to-wall span plus required side clearance, since walls are rarely perfectly square and the cabinet needs a little breathing room.
