Backsplash Calculator
Calculate how many tiles you need for a kitchen backsplash from the counter length and height, plus the square footage to buy, boxes, tile adhesive and cost.
By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- Tiles to buy
- 192 tiles
- 175 tiles of 3 x 6 in plus 10% waste. Buy full boxes from one dye lot
- Area to buy
- 24.8 sq ft
- 22.5 sq ft of wall plus 10% waste
- Tile adhesive (mastic)
- 0.5 gal
- At about 45 sq ft per gallon with a 3/16 in V-notch trowel. Thinset instead for glass, stone and the wall behind the range
Backsplash formula
Area (sq ft) = Counter length (ft) x Backsplash height (in) / 12 + extra area
Tile footprint (sq in) = (Tile width + grout gap) x (Tile length + grout gap)
Tiles = Area x 144 / Tile footprint x (1 + waste %), rounded up
Mastic (gal) = Area / 45Worked example
A 12 ft counter with an 18 in backsplash and 6 sq ft of extra tile up to the range hood, using 4 x 12 in tile with a 1/8 in joint: 12 x 18 / 12 = 18 sq ft, plus 6 = 24 sq ft, or 3,456 sq in. Each tile occupies 4.125 x 12.125 = 50.02 sq in. 3,456 / 50.02 = 69.1 tiles. Add 10% waste: 69.1 x 1.1 = 76.01, so buy 77 tiles, or 2 boxes of 40.
Buy 24 x 1.1 = 26.4 sq ft of tile. Mastic: 24 / 45 = 0.53 gallons, so one 1 gallon tub. At $8 per sq ft the tile costs 26.4 x 8 = $211.
Quick reference
| Counter length | Area | Tiles | Tiles with 10% waste |
|---|---|---|---|
| 8 ft | 12 sq ft | 94 | 103 |
| 10 ft | 15 sq ft | 117 | 128 |
| 12 ft | 18 sq ft | 140 | 154 |
| 15 ft | 22.5 sq ft | 175 | 192 |
| 20 ft | 30 sq ft | 233 | 256 |
| 25 ft | 37.5 sq ft | 291 | 320 |
How to measure a backsplash
Measure the length of every wall section that will get tile, including short returns beside a window or refrigerator, and add them up. Multiply by the height from the counter to the bottom of the upper cabinets, normally 18 in, to get the area in square feet. If the tile runs up to the range hood or continues on a wall with no cabinets, measure that rectangle separately and add it as extra area.
Do not subtract outlets and switches; each one costs 4 to 6 cut tiles, and that is where the waste goes. A 10% allowance covers a running bond with a handful of outlets. Go to 15% for herringbone, diagonal or a window in the middle of the field. Tile sells by the full box, about 10 to 12.5 sq ft for 3x6 subway, from one dye lot; keep the leftover box, since a later order will not match.
Adhesive, layout and finishing
Type 1 mastic (ANSI A136.1), AcrylPro or MAPEI Type 1, is right for ceramic and porcelain up to about 12 in on a dry kitchen wall. Spread it with a 3/16 in V-notch at about 45 sq ft per gallon. The data sheets exclude glass, natural stone and high-heat surfaces. Behind the range and for glass or stone use a white polymer-modified thinset (ANSI A118.4) such as VersaBond; a 50 lb bag with a 1/4 in square notch covers roughly 95 sq ft.
Check the counter with a 4 ft level. If it is out more than 1/8 in over the run, snap a level line one tile plus a joint above the high point. Cut the bottom course to fit; the caulk joint hides the taper. Center the layout on the window or the range hood so the corner cuts come out equal. Kill the breaker and add box extenders (Arlington BE1 type) so receptacles sit within 1/4 in of the tile face (NEC 314.20). The counter joint and inside corners are changes of plane and get color-matched silicone or siliconized acrylic caulk, not grout (TCNA EJ171). Grout is unsanded under 1/8 in and for glass, sanded at 1/8 in and wider; seal cement grout after 72 hours.
What this calculator leaves out
Grout, roughly one 10 lb box of unsanded per 50 to 70 sq ft of 3x6 at 1/16 in; edge trim by the linear foot; box extenders, typically $2 to $5 each; caulk and grout sealer. Removing an old 4 in splash and patching the drywall comes first. Special-order tile runs 2 to 6 weeks with 15 to 25% restocking, and glass or stone needs a wet saw, typically $50 to $75 a day to rent.
Mistakes that cost money
- Tiling over outlets without box extenders leaves receptacles recessed past the 1/4 in NEC 314.20 allows; buy extenders before the tile goes up.
- Starting the first course on an out-of-level counter throws every joint off by the top row; snap a level line and cut the bottom course.
- Grout at the counter joint cracks within a year; the change of plane gets color-matched silicone or siliconized acrylic caulk (TCNA EJ171).
- Mastic under glass tile shows through and never fully cures; glass, stone and anything behind the range get white polymer-modified thinset (ANSI A118.4).
- Handmade-look tile at a 1/16 in joint shows every size variation as a crooked line; those tiles need 1/8 in and sanded grout.
- Buying 22.5 sq ft when boxes hold 10 sq ft gets you 20 or 30; order full boxes from one dye lot and keep leftovers.
Key facts
- A 3 x 6 in subway tile covers 18 sq in, so there are 8 tiles per square foot before grout joints and waste.
- The standard backsplash height is 18 in, the gap between a 36 in counter and upper cabinets hung at 54 in.
- Tile mastic covers about 45 sq ft per gallon with a 3/16 in V-notch trowel, the usual choice for ceramic wall tile up to 12 in.
- Mosaic sheets are 12 x 12 in, so one sheet covers 1 sq ft; a 4 x 12 in tile takes 3 per square foot.
- Add 10% waste for a running bond layout and 15% for herringbone, diagonal or a wall with several outlets.
Frequently asked questions
Do I have to remove the old 4 in backsplash before tiling?
Yes, if the tile is to run to the counter. Cut the caulk and pry the laminate or stone splash off with a putty knife, then scrape the adhesive. Patch the drywall with setting-type compound and tile down to a caulk joint at the counter. Tiling above the old splash reads as an afterthought and leaves a joint at the change of plane that cracks.
How many 3 x 6 subway tiles do I need for 30 square feet?
About 233 tiles with a 1/16 in grout joint, or 256 with 10% waste. Without joints it works out to exactly 8 tiles per square foot.
Should I use mastic or thinset for a backsplash?
Mastic is fine for ceramic and porcelain tile on a dry kitchen wall and spreads about 45 sq ft per gallon. Use thinset for glass, stone, large tile, or directly behind a range where heat and steam are constant.
How high should a backsplash be?
The standard is 18 in, the space between a 36 in high counter and upper cabinets at 54 in. Behind the range it usually continues up to the hood, about 30 in above the cooktop.
Sources and references
- AcrylPro Professional Tile Adhesive product page (Custom Building Products)
- AcrylPro Professional Tile Adhesive technical data sheet TDS-127 (Custom Building Products)
- Type 1 ceramic tile mastic product page (MAPEI)
Next steps for this project
The usual order for a flooring & tile project. See all flooring & tile calculators.
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Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.