How to Measure for a New Bathroom Vanity (Width, Depth, Plumbing Rough-In)

To measure for a bathroom vanity, you need four things: the usable wall width, the depth you can give up without blocking a door or toilet, the finished height you want, and the exact location of the drain and water supply lines. Measure each one at more than one spot, write everything down in inches, and take a photo of the wall with a tape measure in the shot.

What You Need Before You Start

• 25-foot tape measure
• 4-foot level
• Pencil and a notepad (or a sketch on graph paper)
• Phone camera
• Painter’s tape for marking the floor and wall

If the old vanity is still in place, take your measurements with it removed if you can. The cabinet hides out-of-level floors, bowed walls and plumbing that isn’t where you think it is.

Step 1: Measure the Wall Width

Measure the full width of the wall where the vanity goes at three heights: near the floor, at about 30" and at about 36". Old walls are rarely square, and corners often have a buildup of drywall mud that eats up width.

Use the smallest of the three numbers.

Then decide how much space the vanity actually gets:

• Alcove (wall to wall): Subtract at least 1/4" to 1/2" so the cabinet can slide in. If the walls are badly out of square, plan on a filler strip or a scribe so the gap can be closed neatly.
• One side open: Leave room for the countertop to overhang the open end slightly, and check that nothing (a door casing, a towel bar, a light switch) sits in the way.
• Next to a toilet: Measure from the center of the toilet flange (the bolts on the floor) to where the vanity side would land. Many building codes call for at least 15" from the toilet centerline to the nearest side obstruction, and a clear space in front of the toilet. Confirm the exact requirement with your city or county building department.

Common stock vanity widths are 24", 30", 36", 48", 60" and 72". A made-to-size vanity doesn’t have to land on those numbers, so give us the real measurement.

Step 2: Measure Available Depth

The most common vanity cabinet depth is 21", with the countertop running about 22" deep. Narrow-depth vanities around 18" are common in tight bathrooms.

To check depth:

1. Measure out from the back wall to the edge of the door swing, the tub edge or the toilet front.
2. Make sure the bathroom door clears the vanity top and any hardware when it swings open.
3. Check that drawers will clear the toilet or tub when they’re pulled all the way out. A 21" deep drawer box needs roughly that much clear space in front of the cabinet.

Mark the proposed footprint on the floor with painter’s tape and live with it for a day. It’s the cheapest way to find out a vanity feels too big.

Step 3: Decide on Height

Traditional vanities finish around 30"–32" with the top on. Comfort-height vanities finish around 34"–36", closer to kitchen counter height. If you’re using a vessel sink, the bowl sits on top of the counter, so the cabinet usually needs to be shorter.

Also check:

• Height of the bottom of the mirror or medicine cabinet
• Height of any outlet or switch on the vanity wall (a backsplash can run into it)
• Window sills on the vanity wall

Step 4: Locate the Plumbing Rough-In

This is the measurement that causes the most trouble. Measure every one of these from a fixed reference: the finished floor and one side wall (or the centerline of the space).

A few things to watch for:

• Floor drains limit your options. A floating vanity needs a wall drain, and a drawer bank directly over a floor drain won’t work without a plumber relocating it.
• Off-center plumbing is common in older homes. If the drain is several inches off center, tell us so we can plan the sink location and any drawer notches around it.
• High drains can interfere with a top drawer. If you want drawers, the drain location tells us whether you need a U-shaped drawer or a shallow top drawer.

Step 5: Check the Floor and Wall

Set your level on the floor where the vanity goes, front to back and side to side. Note which way it slopes and roughly how much. Then hold the level vertically on the wall. A bow or lean affects how tightly the cabinet back and top sit against it.

Small amounts of out-of-level are normal and get handled with shims and an adjustable toe kick. Big amounts are worth knowing about before you order.

What to Send Us With Your Order

When ordering a made-to-size vanity, send a simple sketch with:

• Wall width (smallest reading) and whether it’s an alcove, open on one side or freestanding
• Desired width, depth and finished height
• Drain and supply locations with heights
• Toilet centerline location, if it’s next to the vanity
• Door swing direction
• Photos of the wall, floor and plumbing

If you’re hiring an installer or plumber, have them check your numbers before you order. We’re glad to coordinate dimensions and drawings with them by email.

FAQ

What is the standard depth of a bathroom vanity? About 21" for the cabinet, with a countertop around 22" deep. Narrow vanities around 18" deep are common in small bathrooms.

Do I measure the old vanity or the wall? Measure the wall. The old vanity may have been undersized, oversized or installed around a problem you’d rather fix.

How much clearance do I need beside a toilet? Many codes call for at least 15" from the toilet centerline to a side obstruction. Confirm with your local building department before you finalize the width.

What if my drain is off center? That’s fine. Give us the exact location and we’ll lay out the sink and drawers around it.

Ready to Order?

Browse our Vanities category to see available styles and sizes, and request finish samples before you commit to a color. If your measurements don’t fit a standard size or you’re not sure about your plumbing layout, email your sketch and photos to information@craftedcabinet.com and we’ll help you sort it out.