Tile Calculator
Tiles, boxes and grout by the TCNA law — the joint volume computed, not guessed.
Tile Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- One tile size per field — mosaics and blends by hand.
- Sanded grout density only; epoxy named, not priced.
- Thinset named as a rule of thumb, not a take-off.
In short: An 80-ft² bath in 12×12 porcelain: 88 tiles ordered at 10%, 7 boxes at 14 ft². Grout: 25.3125 lb by the TCNA law → 2 bags of 25 lb with waste.
Formula
tiles/ft² = 144 ÷ (tile × tile)
order = ⌈field × (1 + layout waste)⌉
grout lb = (W+L)/(W×L) × joint × depth × 0.1875 × ft²×144
bags = ⌈grout × 1.10 ÷ 25⌉
[('144', 'square inches per square foot — the field law'), ('0.1875', 'lb per in³ of sanded grout'), ('10/15/20%', 'straight / diagonal / large-format waste'), ('dye lot', 'one production run per floor')]
Worked Example
- Field the room by the 144 law.
- Waste by layout, ceil to whole tiles.
- Box it by the label’s coverage.
- Weigh the joint with the TCNA law; bag it.
- Price the boxes; budget the thinset.
The 80-ft² bath: 80 field × 1.10 = 88 tiles → 7 boxes ($322.00 at $46); grout 25.3125 lb exact → 2 bags with waste. The joint volume is geometry; the bags are the geometry bought.
Strengths & Limits Of This Model
Where this engine is strong
- Grout by the TCNA law, not the guess
- Layout waste chosen by the pattern
- Box and dye-lot discipline enforced
Where it stops
- One module per computation
- No thinset or membrane line
Practical Use Cases
Bathroom floors
Field and joint in one order.
Backsplashes
Small tile, big joint math.
Large format
The 20% chip for 24×24 floors.
Herringbone
Waste priced before the setter starts.
Grout orders
Bags by law, not by vibes.
Methodology & Editorial Standards
The field follows the exact 144 law; layout chips waste it (10/15/20) and the order ceils to whole tiles and boxes by entered box coverage. Grout follows the TCNA handbook law at 0.1875 lb/in³ sanded, with a 10% waste ceiling into 25-lb bags. Zero faces, joints, or thickness are refused.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Tile Calculator — 10 Expert FAQs
10 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How many 12x12 tiles do I need for 80 square feet?
Exactly 80 in the field (144 ÷ 144 = 1.0 per ft²) — 88 ordered at 10% straight-lay waste, 7 boxes at 14 ft². Diagonal or herringbone takes the 15% chip instead.
How much grout do I need per square foot?
It depends on tile size, joint width and depth — the TCNA law: (W+L)÷(W×L) × joint × depth × 0.1875 lb/in³. For 12×12s at ⅛-in joints: about 0.32 lb/ft²; at ⅜ joints, 0.47.
How much waste should tile carry?
10% straight, 15% diagonal or herringbone, 20% for large-format plank layouts — every one of those cuts edges that cannot be reused. Breakage rides the same chip.
What joint width should I use?
A quarter of an inch forgiving, a ⅛-inch sharp: rectified porcelain takes tight joints, handmade and quarry tile wants width. The grout law prices either honestly.
How much thinset per square foot?
A 50-lb bag covers roughly 60-80 ft² at the ¼-inch notch; large formats on ½-inch notches drink faster. Back-butter large tile or the coverage is fiction.
Sanded or unsanded grout?
Sanded for joints ⅛-inch and wider — the sand stops shrink-cracks. Unsanded for tighter joints and easily scratched stone. Epoxy for chemicals and commercial kitchens, at a different price planet.
Why order a full box over the count?
Tiles ship per box and break in transit — but the real reason is dye lot: production runs drift in tone, and a future box will not match a floor laid today. One run, whole floor.
Do I need backer board under tile?
On floors over wood framing and any wet wall — yes. Tile flexes and cracks with the substrate; cement board or a bonded membrane is what makes the field last. The tile count does not change; the assembly does.
How long before grouting or walking on tile?
Thinset typically wants about 24 hours before grout, and grout about a day before light traffic — the products’ datasheets rule. Flood the schedule with rain delays and cold floors.
Is heated floor worth it under tile?
Tile holds heat beautifully, which is why electric mat systems under bathroom fields are so loved — budget it as its own line before the thinset, not after the tile is down.