Backsplash Tile Calculator: How to Measure It and What to Buy

How to measure a backsplash

Seven measurements, in this order. Take them all in inches and write them down as inches; convert once, at the end, rather than juggling feet and fractions as you go.

1. Sketch the runs. One line per wall that is getting tile. Most kitchens have two or three: the sink run, a return along the next wall, and the wall behind the range.
2. Measure each run along the wall, end of counter to end of counter — the stretch of wall that has countertop under it, which is usually shorter than the wall itself. Where two runs meet at an inside corner, measure each one up to the corner and add them: the tile turns the corner, so the two lengths meet on a line and nothing is counted twice.
3. Measure the height in three places on each run, both ends and the middle. Countertops and wall cabinets are rarely parallel, and 18 inches at one end can be 17 3/4 at the other. Order for the largest and expect the top course to be scribed.
4. Measure the range wall separately, countertop to the underside of the hood, and note its width. It is taller than everything else, and its width has to come out of the main run so the area is not counted twice. The calculator above does that subtraction for you.
5. Measure any window opening in the run, width and height. The tile stops at the sill and the jambs, and both edges need trim.
6. Count the outlets and switches. Not their size — just how many. They add tile rather than saving it, for a reason worth reading further down.
7. Measure the exposed edges: every place the tile stops in mid-air rather than dying into a cabinet or a wall.

Then the arithmetic, which is the part people are usually looking for:

square feet = (total run in inches x height in inches) / 144

Fourteen feet of counter is 168 inches; at 18 inches high that is 168 x 18 / 144 = 21 square feet, and that figure is the main run on its own. Work the range wall out the same way at its own height and add the two, remembering to take its width out of the 14 feet first so that strip is not paid for twice.

The 15 percent rule is hiding something

Every guide on this subject ends the same way: work out the area, add 10 or 15 percent, order that. Fireclay Tile's measuring lesson says 15 percent. Apollo Tile says at least 10.

Keep the allowance. But it is doing two different jobs, and only one of them is genuinely a percentage. Breakage, a spare box in the right dye lot, and the tiles you will want in five years when a cabinet gets replaced all scale with the size of the order. The cutting does not.

On a floor, cuts happen around the edge of the room, so their share shrinks as the room grows. A backsplash has no middle. At the standard 18 inches it is anywhere from one course to eight, depending on the tile, the top course is almost always a rip, and what that rip costs is set by one division you can do standing at the counter: your height, divided by the height of the tile as laid, plus the joint.

Here is the same tile on the same 14 feet of counter, laid the usual way with the long side horizontal, and with nothing changed but the height. The counts are tiles actually cut and set, with no allowance on top — the calculator above adds its 15 percent to figures like these, so it will always ask for more:

Two things fall out of that table that no percentage can tell you. Going from 17 inches to 18 costs nothing — both need 168 tiles, because both leave you ripping one course, just at a different width. And going from 15 inches to 21 costs 40 percent more tile, 140 pieces against 196, for six inches of wall.

The tile matters as much as the height. At the standard 18 inches:

There is a threshold worth knowing in there. If the last course is less than half a tile, one tile gives you two strips and the rip costs half as much; if it is more than half, each strip eats a whole tile. With 3 x 6 subway at 19 inches the last course is 11/16 of an inch and you get two strips from every tile. At 20 inches it is 1 11/16 and you do not.

Half a sheet is the best number and the worst number

At the standard 18 inches a 12-inch mosaic sheet leaves a last course of exactly six inches. Half a sheet — right on the threshold. Which way it falls depends on something the measurement cannot see.

For a solid 12 x 12 tile, half is the worst case. You rip every tile down the middle, the blade takes an eighth of an inch, and a sawn edge cannot be the edge that shows, so the offcut is scrap. Cut waste comes out around 35 percent, more than double the allowance everyone recommends, and a 15 percent order leaves you short.

For a mosaic sheet, half is the best case. You do not cut a sheet, you separate it: the mesh parts along a joint line, both halves are finished on all four edges, and the waste is about 1 percent.

Same height, same nominal size, same measurement, and one of them takes a third more material than the other: 28 pieces cut and set against 21, for the same 14 feet of counter. What decides it is whether the joints run through the material.

The standard 18 inches, and the exceptions

Eighteen inches is the usual distance from countertop to upper cabinets in American kitchens, and filling it completely is the default look. Two things break that rule:

• The range wall. Where there is a hood rather than a cabinet, the tile usually runs the full height to the underside of the hood — often 30 inches or more. That section is taller than the rest and gets its own field in the calculator, then it is removed from the main run so it is not counted twice.
• A window over the sink. Tile runs to the sill and stops, which means less area and more trim.

Measure yours rather than assuming. Older kitchens vary a lot, and a countertop that was replaced without moving the cabinets can leave anything from 15 to 20 inches.

Outlets cost tile, they do not save it

This is the single most common way to end up one box short.

The instinct is to deduct the outlets from the area, the way you would deduct a window from a wall. It is exactly backwards. An outlet box sits in the middle of a tile far more often than it lines up with a joint, so you cut a hole through a tile and the remainder is scrap. A four-outlet kitchen backsplash does not save you a square foot — it costs you around six tiles.

The calculator adds them as waste for that reason, at about 1.5 pieces per box. Four outlets, six extra tiles.

If you have any say over it, a related tip: outlet boxes can often be rotated to horizontal, which puts the cut in a much less awkward place and can turn two ruined tiles into one.

Sheets and pieces behave differently

Subway tile is sold by the piece and behaves like any other wall tile. Mosaic and most patterned tile come as sheets — usually 12 by 12 inches on a mesh backing — and they behave differently in three ways:

1. You can cut a sheet down and use both halves, so mosaic wastes less than the calculator suggests. The result is deliberately on the conservative side here.
2. The joints between sheets have to disappear. A sheet layout that is not carefully aligned leaves a visible grid of slightly wider joints every 12 inches. Take the time to work the edges together before the mortar grabs.
3. Mosaic uses far more grout than the same area of large tile — often ten times as much, because grout volume follows the total length of joint. If you are doing a mosaic backsplash, size the grout properly rather than guessing.

Where the tile stops

Backsplashes almost always have at least one edge hanging in mid-air: the end of a run, or the top edge where there are no upper cabinets. That edge needs finishing, and the options are the same as any wall — a metal profile bedded in as you tile, a bullnose piece if the range makes one, or a mitre.

The one thing you cannot do is decide afterwards. A metal profile goes in with the field, not onto it.

Trim is estimated here at the exposed run plus 10%. Profiles typically come in 8 and 10 foot lengths, so round up to whole sticks and expect one to be mostly offcut.

Behind the appliances

• Behind a slide-in range: tile it. The gap is visible from the side, and the next range will be a slightly different height.
• Behind the fridge: do not. Nobody sees it.
• Behind a freestanding dishwasher: no, but do run the tile down to the countertop line so a future counter change does not expose bare wall.

The order of work

Backsplash tiling has one sequencing rule that matters more than the rest: the countertop goes in first, and the tile sits on it.

Tiling down to a line and then sliding a countertop underneath leaves a gap you will be caulking forever. Tile onto the finished counter with a small expansion gap at the bottom, filled with a flexible caulk rather than grout, because the counter and the wall move independently and grout will crack along that line every time.

The same applies where the backsplash meets an inside corner: caulk, not grout.

A worked example

A kitchen with 14 linear feet of counter, 18 inches high, including a 30 inch range section running 30 inches tall, four outlets, 3 × 6 subway tile with 1/16 inch joints, and 3 feet of exposed edge.

• Range section: 2.5 ft × (30 ÷ 12) = 6.25 sq ft
• Main run: (14 − 2.5) × (18 ÷ 12) = 17.25 sq ft
• Total area: 23.5 sq ft
• Module: 3.0625 × 6.0625 ÷ 144 = 0.129 sq ft → bare coverage 183 tiles
• With 15% waste: 211, plus 6 for the outlets = 217 tiles
• Trim: 3 linear feet plus 10% — one 8 foot profile

Twenty-three square feet of wall, and well over two hundred individual pieces to cut, butter and set. That ratio is why backsplashes take longer than people expect.