Measure the shower inside: the wall the bench goes on, and from that wall to the other side. You get the bench’s height and depth, and whether the shower still meets the code with it.
Shower bench
An 18″ high, 15″ deep bench36″ long · leaves 1,188 sq in and 33″ in front: the code’s 900 sq in and 30″ ✓
Quick answer: a shower bench’s top goes 17–19″ above the shower floor and it is 15″ deep (NKBA guideline 12; ADA §610.3). It must leave the shower its code minimum of 900 sq in and 30″ across (IRC P2708.1), so a built-in bench needs a shower at least 45″ from its wall to the other side; in a smaller shower, a fold-down seat counts folded up.
How to use the shower bench calculator
- Pick a built-in bench or a fold-down seat.
- Measure the shower inside, finished wall to finished wall: the wall the bench goes on, and from that wall to the other side (the glass or the curb).
- Give the bench’s length if it does not run the whole wall.
- Read the height, the depth and the check. Copy link keeps the result.
The rules behind the numbers
Height and depth
The National Kitchen & Bath Association’s bathroom planning guideline 12: “Plan a seat within the shower that is 17″–19″ above the shower floor and 15″ deep.” The ADA Standards say the same for an accessible shower: the seat’s top 17–19″ above the floor (§610.3), its front edge 15–16″ from the wall (§610.3.1), running from the back wall to within 3″ of the entry, and strong enough for 250 lb at any point (§610.4).
The code’s minimum shower
The IRC asks every shower for at least 900 sq in inside and 30″ in its least dimension, measured from the top of the threshold “to a height of not less than 70 inches above the shower drain outlet” (P2708.1). A built-in bench sits inside that space, so the NKBA puts it plainly: the seat “must not infringe on the minimum interior size of the shower”. The calculator takes the bench’s footprint out and checks what is left, read strictly: 900 sq in, and 30″ clear in front of the bench.
Fold-down seats
The code’s own exception: “Fold-down seats shall be permitted in the shower, provided that the required 900-square-inch dimension is maintained when the seat is in the folded-up position.” That is why a small shower can still have a seat.
A 15″ bench in common shower sizes
| Shower | Bench on the short wall | Bench on the long wall |
|---|---|---|
| 32 × 32″ | no: fold-down | no: fold-down |
| 36 × 36″ | no: fold-down | no: fold-down |
| 42 × 42″ | no: fold-down | no: fold-down |
| 48 × 32″ | yes | no |
| 48 × 36″ | yes | no |
| 60 × 36″ | yes | no |
| 60 × 42″ | yes | no |
A whole-wall bench, 15″ deep, read strictly (30″ clear in front, 900 sq in left). On the short wall of a long shower, a bench fits from 45″ deep.
Three worked examples
A 48 × 36″ shower, the bench on the 36″ wall. An 18″ high, 15″ deep bench, 36″ long: it leaves 1,188 sq in and 33″ in front. It passes.
A 60 × 36″ shower, the bench along the 60″ back wall. Only 21″ would be left in front of it, under the code’s 30″. On the 36″ end wall the same bench fits.
A 36 × 36″ shower. No built-in bench fits, but a fold-down seat does: folded up, the shower keeps all 1,296 sq in.
Common shower bench mistakes
- A bench too low. Under 17″ is hard to stand up from; 18″ sits in the middle of the range.
- A bench that shrinks the shower below the code. Check what is left, especially on a long back wall.
- Forgetting the slope. Slope the bench’s top toward the shower so water runs off it.
- A seat nobody can reach the controls from. Put the valve where a seated person can reach it (the bathroom accessory height calculator places it).
Planning the rest of the shower? The free shower niche calculator sets the niche over the bench, the bathtub and shower size finder sizes the shower itself, the bathroom accessory height calculator places the valve and the grab bars, and the free 2D room planner draws the bathroom to scale.
Size the showerRead next
Shower bench questions
What is the standard shower bench height?
17–19″ from the shower floor to the top of the seat (NKBA guideline 12; ADA §610.3). 18″ is the middle of that range.
How deep should a shower bench be?
15″ (NKBA); an accessible seat 15–16″ from the wall to its front edge (ADA §610.3.1).
What size shower do you need for a bench?
With a 15″ built-in bench, the shower must still have 900 sq in and 30″ in front of the bench (IRC P2708.1): at least 45″ from the bench wall to the other side. A 48 × 36″ shower takes one on its 36″ wall.
Does a shower bench count toward the minimum shower size?
A built-in bench does not: the code measures the shower up to 70″ above the drain, and the NKBA says the seat must not infringe on the 900 sq in. A fold-down seat counts folded up.
What are standard shower bench dimensions?
17–19″ high and 15″ deep, as long as the wall it sits on or shorter; an accessible seat runs from the back wall to within 3″ of the entry.