Bathtub & Shower Size Finder

How to use the bathtub and shower size finder

1. Pick what goes there: an alcove tub (between three walls), a freestanding tub, or a shower.
2. Measure wall to wall along the back wall. For a tub or shower base built in, that length IS its size.
3. Measure out from the back wall to the opposite wall, or to the front of the vanity or toilet across from it. The tub’s width and the floor you step onto both come out of this.
4. Say where you measured. Over finished tile, or at bare studs in a gutted room: a built-in tub goes in before the tile, so the two differ. Copy link keeps the result.

The rules behind the sizes

An alcove tub is as long as the space

An alcove tub is built in wall to wall, so the space decides its length. American Standard sells alcove tubs from 54 to 72 inches; the standard, in tub maker Badeloft’s words, is “60 inches long, 30 to 32 inches wide”. The sizes here are each on a maker’s list: 54 × 30 (Kohler Seaforth), 60 × 30, 32, 34 and 36 (American Standard, Kohler Underscore), 66 × 32 (Kohler Archer and Bellwether) and 72 × 36 (Kohler Avec).

Measured over the tile, add it back

Badeloft again: “A 60 inch alcove is a stud-to-stud dimension. Add half-inch backer board and tile on both walls and the visible, finished opening comes out somewhere between 57.75 and 59 inches. The tub still fits, because the tub goes in first.” So a tiled opening takes a tub 1 to 2¼″ longer than it measures. A shower base goes in before the tile the same way.

30″ of clear floor to step out onto

The National Kitchen & Bath Association (NKBA) plans 30″ of clear floor in front of a tub or shower, along its length. The building code’s least is 21″ in front of a tub and 24″ in front of a shower. The finder takes the 30″ unless you pick the code minimum.

A freestanding tub needs air round it

Freestanding tubs run about 55 to 75″ long and 26 to 47″ wide. Badeloft leaves “six to twelve inches between the tub and any wall or fixture on the other three sides” (you have to clean back there), and 30″ of clear floor along the side you step in from.

The shower: 30″ × 30″ by code, 36″ × 36″ to be comfortable

The International Residential Code (2024, P2708.1) wants a shower of at least 900 square inches inside and 30″ across its narrowest side; a 25″-wide one passes if it has 1,300 sq in. Its way in must be at least 22″ clear. The NKBA recommends 36″ × 36″ inside. A tiled shower can be any size; a base must be one that is sold.

Alcove bathtub size chart

Shower base size chart

Also sold: 36 × 42″ (42″ deep), 42 × 34″, 48 × 34″, 54 × 34″ and 60 × 34″. Every base here is bigger than the code’s 900 sq in; check a base’s drawing for its inside size at the curb.

Three worked examples

A tiled alcove, 58½″ wall to wall and 60″ out to the vanity. Tile and backer took 1–2¼″ off the studs, so this opening held a 60″ tub. With 30″ of floor left in front, only the 30″-wide one fits: a 60″ × 30″ alcove tub. Check the studs or the old tub before you buy: the 60″ fits only if the tile took 1½″.

A shower in a 36″ space, 66″ out to the far wall. The biggest base that fits is 36″ × 36″, the NKBA’s size, and it leaves 30″ of floor in front. A 32″ × 32″ fits too, but only just clears the code.

A freestanding tub in a 7-foot space, 72″ out. With 6″ from each end wall, 6″ behind and 30″ in front, the tub can be up to 72″ × 36″; for a foot of air round it, 60″ × 30″.

Common bathtub and shower sizing mistakes

• Buying the tiled opening’s size. A tiled 58½″ opening held a 60″ tub; a 58″ tub leaves a gap at the end. Measure the old tub, or the studs.
• Forgetting the floor in front. A 36″-wide tub in a 60″-deep bathroom leaves 24″ to step out onto, under the 30″ planned for.
• Pushing a freestanding tub against the wall. Without 6″ round it you cannot clean behind it, and a floor-mounted filler needs its own room.
• A shower under 30″ across. It fails the code however long it is, unless it is at least 25″ across and 1,300 sq in inside.
• Measuring once. Walls are rarely straight: Badeloft measures “at the front, the middle and the back, at more than one height”, and uses the smallest number.

Read next

• Soaking tub-shower combos
• Walk-in shower ideas
• Small shower ideas
• Tub tile ideas
• Shower tile combinations

Bathtub and shower size questions

What is the standard bathtub size?

60″ long, 30 to 32″ wide (152 × 76–81 cm), and 14 to 18″ tall. That is the alcove tub built wall to wall into a 5-foot space, with 30″ of floor in front to step out onto.

How long is a standard tub?

60″. Alcove tubs are sold from 54 to 72″ long: 54″ for a small bathroom, 66 and 72″ for a taller bather. Freestanding tubs run about 55 to 75″.

What size is a small bathtub?

54″ × 30″ is the smallest alcove tub the big makers sell (Kohler’s Seaforth, for one). It needs 54″ at the studs and 60″ out from the back wall, with 30″ of floor in front.

What is the standard shower size?

The NKBA recommends 36″ × 36″ inside. The code’s least is 30″ × 30″ (900 sq in). Shower bases are sold from 32″ × 32″ to 60″ × 36″, and 60″ × 30–36″ bases fit where a standard tub was.

What is the minimum shower size?

By the International Residential Code, 900 square inches inside and 30″ across the narrowest side, so 30″ × 30″. A 25″-wide shower passes if it has at least 1,300 sq in, such as 25″ × 52″. The way in must be at least 22″ clear.

What are the standard shower pan sizes?

32 × 32, 36 × 36 and 42 × 42″ square; 48 × 32, 48 × 34 and 48 × 36″; 60 × 30, 60 × 32, 60 × 34 and 60 × 36″ long. The first number is the width along the back wall, the second the depth.

How big is a walk-in shower?

Most start from a tub’s footprint: a 60″ × 30–36″ base, which leaves the rest of the bathroom as it was. Any shower must still be at least 30″ × 30″ inside, with 30″ of floor in front to step out onto.

How much space do you need for a freestanding tub?

Its length plus 12 to 24″ wall to wall (6 to 12″ each end), and its width plus 36″ out from the back wall (6″ behind, 30″ to step in). A 60″ × 30″ tub needs a space about 72″ by 66″.