Backsplash Tile Calculator

How this is calculated

THE STANDARD GAP IS 18 INCHES. Worktop to the underside of the wall cabinets is 18 inches in most kitchens, which is the height of your main run. Measure yours rather than assuming - 15 and 20 both exist, and on a 12 foot run a 2 inch difference is 2 square feet. THE COOKER WALL IS TALLER. Behind a range or hob the tile usually runs up to the extractor rather than stopping at cabinet height, so it is a separate rectangle - commonly around 30 inches tall and the width of the appliance. It is easy to forget and it is a meaningful fraction of a small job. THE ARITHMETIC: (run length x height) + (cooker width x cooker height) - openings, plus waste, divided by the coverage of one box. ⚠️ BOX ROUNDING DECIDES WHAT YOU BUY, NOT THE WASTE PERCENTAGE. This is the same lesson as the flooring calculator and it bites harder here because the job is so small. A 21.5 square foot backsplash with 10% waste is 23.65 square feet - but tile comes in boxes, and at 10 square feet a box you buy 3 boxes and 30 square feet. That is 39% more than the net area, and no waste setting you choose will change it. WHICH IS FINE, AND YOU SHOULD KEEP IT. Tile is made in dye lots and they do not match between production runs. The spare from your own box is the only tile that will ever match your wall. Put the offcuts and the remainder of the last box somewhere you will find them in five years - it is the difference between replacing one cracked tile and retiling the kitchen. ⚠️ DO NOT DEDUCT SOCKETS AND SWITCHES. You cut the tile around them, so the tile is consumed either way, and the offcut is rarely usable. Only deduct genuinely large openings - a window over the sink is worth taking out, a double socket is not. WASTE: 10% is right for a straight or brick-bond layout in a simple rectangle. Go to 15-20% for a diagonal or herringbone pattern, where every edge tile is a cut and the offcuts are the wrong shape to reuse. Mosaic sheets waste less than you expect because you can cut between the tiles. BUY THE TRIM AT THE SAME TIME. Edge trim, bullnose or a metal profile is what finishes the exposed end of a run, it is sold separately, and it is the single most commonly forgotten item on a backsplash job. Measure the exposed vertical edges and the top edge if it is not meeting a cabinet.

Common questions

How much tile do I need for a kitchen backsplash?

For a 12 ft run at the standard 18 in height, plus a 3 ft wide cooker wall running 30 in up to the extractor, minus a 4 sq ft window: 21.5 square feet. Add 10% waste and you need 23.7 - but tile comes in boxes, so at 10 sq ft a box you buy 3 boxes and 30 square feet. The box rounding, not the waste percentage, is what decides the bill.

How tall is a backsplash?

The standard gap between a worktop and the underside of the wall cabinets is 18 inches, and that is the height of your main run. Measure yours rather than assuming, because 15 and 20 inches both exist and on a 12 foot run a 2 inch difference is 2 square feet - about a tenth of the whole job. The wall behind the cooker is usually taller, running up to the extractor instead of stopping at cabinet height.

Should I deduct sockets and switches?

No. You cut the tile around them, so the tile is consumed whether the socket is there or not, and the offcut from a socket cut is rarely the right shape to use anywhere else. Only deduct genuinely large openings - a window over the sink is worth taking out of the total, a double socket is not. Deducting small openings is one of the ways people end up a box short.

Why do I end up with so much spare?

Because the job is small and boxes are not. A 21.5 square foot backsplash needing 23.7 square feet has to be bought as 3 boxes of 10, which is 30 - about 39% more than the area you are covering. On a large floor that rounding disappears into the total; on a backsplash it is a big proportion. It is not waste you can plan away, and you should not try to.

Is it worth keeping the leftovers?

Yes, and it is the most valuable thing you will have left at the end. Tile is made in dye lots that do not match between production runs, so in three years the same product code from the same shop can be visibly different against your wall. The spare from your own box is the only tile that will ever match. Store the remainder and the usable offcuts somewhere you will actually find them - it is the difference between replacing one cracked tile and retiling the kitchen.

How much waste should I allow?

10% for a straight or brick-bond layout in a simple rectangle. Push to 15-20% for diagonal or herringbone, where every perimeter tile is a cut and the offcuts come out the wrong shape to use elsewhere. Mosaic sheets waste less than people expect, because you can cut between the individual tiles rather than through them. Add more if the run has several corners or an awkward window.

What do I need besides the tile?

Edge trim is the answer people forget. The exposed vertical end of a run and any top edge not meeting a cabinet needs bullnose, a metal profile or a matching trim piece, and it is sold separately from the tile. The calculator gives you a starting figure in linear feet. You will also want more thinset and grout than the tile alone suggests, and a tile cutter that can handle the material - porcelain and natural stone are a different job from ceramic.

Does the cooker wall really need to be separate?

It is worth treating separately because it is a different height, and averaging it into the main run is how it gets lost. Behind a range or hob the tile typically continues up to the extractor rather than stopping at cabinet height, so it is a taller rectangle the width of the appliance. On a small job that patch can be a third of the total area. It is also the area most likely to get a feature tile or a different pattern, which makes keeping it as its own number doubly useful.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Backsplash Tile Calculator at https://www.bfcbrilliance.com/tools/backsplash-tile-calculator.

What I entered:
- Length of the run (ft): ___
- Worktop to cabinets (in): ___
- Width behind the cooker (ft): ___
- Height behind the cooker (in): ___
- Window or opening to deduct (sq ft): ___
- Waste (%): ___
- Coverage per box (sq ft): ___

What it calculated:
- Boxes to buy: ___
- Area to tile: ___
- The main run: ___
- Behind the cooker: ___
- With waste added: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

Where the job touches structure, gas, or electrics, tell me to check local building code and whether a permit or a licensed trade is required.

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