Tile Calculator

Why Tile Estimates Need Extra Care

Tiling is one of the few home improvement jobs where a small calculation error costs you real money twice — once when you run short, and again when you cannot find a matching replacement. This free tile calculator handles the math so you can focus on the install. Enter your room dimensions and tile size, pick a pattern, and it returns total tiles, boxes, grout, and thinset in seconds.

The core problem is waste. Straight-lay tile on a clean rectangular floor wastes roughly 10 percent — mostly from cutting border tiles. Herringbone and diagonal patterns push that number to 15 percent or higher, because every tile at the perimeter gets cut at 45 degrees and the offcuts are too small to reuse. On a 200 sq ft floor, the gap between 10 and 15 percent waste is 10 extra tiles — real money when you're buying $4-per-sq-ft porcelain.

Running short mid-project creates a second problem: dye lots. Tile is glazed in batches, and even the same SKU from the same store looks subtly different if the next shipment came from a different firing. Order everything from one batch. Buy one extra box beyond what the calculator says — a spare tile in the garage is the cheapest insurance you'll ever buy on a renovation.

How to Use This Calculator

1. Enter the area. Use Length × Width for rectangular rooms, or switch to the Area tab for irregular spaces. For L-shaped layouts, calculate each rectangle separately and add them together before entering the total.
2. Select tile size and pattern. Choose a preset tile size from the dropdown or enter a custom length and width in inches. Pick your grout joint width and layout pattern — straight lay and offset apply a 10% waste factor, herringbone and diagonal apply 15%.
3. Review tile count, grout, and thinset amounts. Enter tiles per box from the box label and a price per box to get a total material cost. The results show tiles needed (after waste), boxes to order, grout in pounds, and thinset in pounds. Add one extra box to your cart before you check out.

How to Calculate Tiles Manually

1. Measure the area. Multiply length × width in feet to get square footage. For L-shaped or irregular rooms, split the space into rectangles, calculate each, and add the totals.
2. Calculate single-tile coverage including the grout joint. The formula: (tile length in inches + joint width) × (tile width in inches + joint width) ÷ 144. For a 12×12 tile with a 1/8-inch joint: (12.125 × 12.125) ÷ 144 = 1.021 sq ft per tile.
3. Divide area by tile coverage. 100 sq ft ÷ 1.021 sq ft per tile = 98 tiles before waste. This is your baseline count — do not order this number.
4. Apply the waste factor. Straight or offset layouts: multiply by 1.10. Herringbone or diagonal: multiply by 1.15. Round up to the next whole tile. 98 × 1.10 = 107.8 → 108 tiles.
5. Divide by tiles per box. Round up to a whole box. 108 ÷ 10 tiles per box = 10.8 → 11 boxes. Buy one additional box beyond this total for future repairs.
6. Calculate grout. For 12×12 tiles with a 1/8-inch joint, plan roughly 1 lb of grout per 8 sq ft. Smaller tiles and wider joints consume significantly more — a 3×6 subway tile with a 3/16-inch joint uses closer to 1 lb per 2 sq ft. Always buy 10% extra grout.
7. Calculate thinset. A standard rate is about 0.5 lbs per sq ft for most floor tiles with a ½-inch square-notch trowel. Large-format tiles (12×24 and bigger) need more coverage and back-buttering — budget closer to 0.75 lbs per sq ft. Our drywall calculator can help you size cement board if you're tiling over a new substrate.

Tile Sizes and Coverage

Common Tile Estimation Mistakes

Not accounting for grout joint width. A 1/8-inch joint adds about 1 percent to the coverage area of a 12×12 tile. That sounds trivial, but on a 400 sq ft floor with 9-inch subway tiles and a 3/16-inch joint, the joint width alone adds the equivalent of 30 extra tiles. Always include the joint in your coverage calculation rather than dividing raw tile dimensions into square footage.

Forgetting that herringbone cuts every border tile at 45 degrees. In a straight-lay pattern, border cuts produce usable offcuts you can reuse on the opposite side of the room. In a herringbone pattern, every perimeter cut produces a triangle offcut — too small for anything else. All of those wasted cuts are built into the 15% waste factor, but first-time installers often see the 15% and think it seems excessive. It is not.

Not ordering from the same dye lot. Tile glaze is fired in batches. Two boxes of the same SKU purchased six weeks apart may have a slight color or texture difference that is invisible in the store under fluorescent light and glaringly obvious on your bathroom floor under morning sun. Buy your full order at once, confirm the lot numbers match on every box, and set one box aside for repairs.

Underestimating thinset for uneven surfaces. A flat, freshly poured concrete slab is the best-case scenario. Real subfloors have dips, humps, and old adhesive ridges. Filling those low spots eats thinset fast. Budget an extra 20–25% when tiling over an existing floor, and consider a self-leveling underlayment for anything more than 3/16-inch variation over 10 feet. If you're tiling an outdoor patio or path, the paver calculator handles natural stone and concrete pavers, and the gravel calculator sizes the compacted base beneath them. Switching to a floating floor instead? The vinyl plank flooring calculator handles that layout with its own waste and underlayment estimates.

Frequently Asked Questions

How many tiles do I need per square foot?

It depends on tile size. A 12×12-inch tile covers 1 sq ft, so you need 1 tile per sq ft before waste. A 6×6-inch tile covers 0.25 sq ft, so you need 4 per sq ft. Divide 144 by the tile's area in square inches to find tiles per sq ft for any size.

How much extra tile should I order for waste?

Order 10% extra for straight-lay and offset brick patterns — those cuts are predictable and the offcuts are often reusable. Bump to 15% for herringbone and diagonal, where every border tile is cut at an angle. Add another 5% buffer if this is your first tile install; cutting mistakes happen.

What size grout joint should I use?

Rectified porcelain (machine-cut to exact dimensions) can use joints as tight as 1/16 inch for a near-seamless look. Standard ceramic needs 1/8 to 3/16 inch to absorb slight size variations between tiles. Natural stone and outdoor pavers typically need 1/4 inch or wider for movement tolerance and drainage.

How much grout do I need per square foot?

Coverage varies by tile size and joint width. As a rough rule, 12×12 tiles with a 1/8-inch joint use about 1 lb per 8 sq ft. Small subway tiles with a 3/16-inch joint use closer to 1 lb per 2 sq ft. The calculator does this math automatically — always buy 10% extra for cleanup waste and touch-ups.

Is herringbone tile pattern more expensive?

Yes, in two ways. The 15% waste factor means more tile purchased upfront compared to 10% for straight lay. Labor is also significantly higher — cutting every border tile at 45 degrees takes more time, skill, and saw passes. Expect professional installation costs to run 20–30% more than a comparable straight-lay project.