Wall Tile Calculator: Courses, Cuts and Trim

Walls are counted in courses

A floor is an area problem. A wall is a stacking problem, and the number that decides whether it looks right is not the tile count — it is the height of the row that gets cut.

Every wall ends up with one partial course somewhere, because wall heights are not multiples of tile heights. Where you put it, and how tall you let it be, is the whole game.

The course arithmetic

One course occupies the tile height plus one grout joint:

course height   = tile height + grout joint
full courses    = wall height ÷ course height, rounded down
cut course      = wall height − (full courses × course height)

For a 24 inch tile with a 1/16 inch joint, each course is 24.0625 inches, or 2.005 feet. An 8 foot wall takes three full courses (6.016 feet) and leaves 1.984 feet — 23 13/16 inches — for the fourth. That is nearly a full tile, which is a good outcome.

Move the wall height to 7 feet and you get three full courses and an 11⅞ inch cut. Still fine. Move it to 6 feet 2 inches and you get two full courses and a 25½ inch remainder that will not fit as one piece, so it becomes a full course plus a 1½ inch sliver — and that sliver is what people notice for the next fifteen years.

Slivers, and how to get rid of them

A cut course under about 2 inches, or less than a third of the tile, is a sliver. Three problems with them:

1. They are hard to cut cleanly. A narrow strip of porcelain snaps rather than scores.
2. They are hard to bed flat, because there is not enough surface for the mortar to grab.
3. They draw the eye immediately. A thin line of tile at the top of a wall looks like the wall won.

The fix is to take one full course out of the stack and split the remainder between the top and the bottom. In the 6 foot 2 inch example, instead of two full courses plus a 1½ inch sliver, you run one full course with two cut courses of about 13⅝ inches each. You cut more tile and the wall stops looking like a mistake.

The results above give you both numbers so you can see the trade before you commit.

Where the cut course should go

Bottom, in most rooms.

At floor level, or immediately above a tub or a countertop, a partial course reads as a transition between two materials — which is exactly what it is. The same cut at eye level reads as running out of wall.

The exceptions are walls that die into a ceiling with nothing to break the line, where a thin strip at the top is more conspicuous than one at the bottom, and walls where a strong horizontal feature — a niche, a border, a windowsill — dictates where the full courses have to land.

What to deduct, and what deducting hides

Deduct doors and windows from the area. But remember what the deduction takes away with it: edges.

A window in a tiled wall has a sill, a head and two jambs, and all four usually need finishing with trim or with mitred tile. Deducting 12 square feet of window from the area removes tile you did not need, and simultaneously removes any prompt to buy the twelve linear feet of profile you now do need.

The same goes for a door opening, an outside corner where two tiled walls meet, and the top edge of the tile wherever it stops short of the ceiling.

Trim, and deciding early

Where tile stops in mid-air, something has to finish the edge. Four options, in rough order of how commonly they are used:

The important part is that the first three are decisions you make before the field goes up, not after. A metal profile in particular has to be set into the mortar as the adjacent tile goes on. Discovering you wanted one on Sunday afternoon is discovering it too late.

Getting the vertical right

Two habits separate a wall that looks level from one that is:

• Do not trust the floor. Floors are not level, and a first course laid to the floor will carry that error all the way up, opening a visible wedge against a ceiling or a window head. Find the low point, snap a level line one course up from it, and hang the first full course to that line. The cut course underneath absorbs the floor's error.
• Check the ledger and the plumb regularly. Tile drifts. Check the horizontal every couple of courses and the vertical every few tiles, because errors are cheap to fix while the mortar is soft and impossible afterwards.

A worked example

A bathroom with 12 linear feet of wall tiled to 8 feet, no openings, using 12 × 24 tile stacked vertically with 1/16 inch joints and 3 feet of exposed outside corner needing trim.

• Net area: 12 × 8 = 96 sq ft
• Course height: 24 + 0.0625 = 24.0625 in = 2.005 ft
• Full courses: 8 ÷ 2.005 = 3.99 → 3 full courses
• Cut course: 8 − (3 × 2.005) = 1.984 ft = 23 13/16 inches

That is a fat cut, so there is no sliver to solve and no reason to drop a course. Had the wall been 6 feet 2 inches, the same tile would have left 1½ inches and the sensible move would have been two cut courses of about 13⅝ inches instead.

• Module: 12.0625 × 24.0625 ÷ 144 = 2.016 sq ft → bare coverage 48 tiles
• With a 15% wall allowance: 55 tiles, or 8 boxes at 15.5 sq ft per box
• Trim: 3 linear feet plus 10%, in whatever length the profile comes in