Tile Calculator
Enter your room and tile size to get the exact tile count, grout and thin-set estimate — with the right waste factor for your layout pattern and every formula shown.
Your floor
Add an L-shape or extra room as another area — totals are summed.
Tiles to buy
198 tiles
- Total area
- 180 ft²
- Grout (estimate)
- 1 × 25 lb bag
- Leftover (attic stock)
- 18 ft²
- Grout is an estimate — yield varies by tile and product. Confirm against the bag's coverage chart.
- Buy all boxes at once so they share a dye lot, and keep the leftover as attic stock for future repairs.
How this is calculated
Total area
Σ (length × width)
= 12×15
180 ft²
Add waste
area × (1 + waste% ÷ 100)
= 180 × (1 + 10 ÷ 100)
198 ft²
Tile area
(tile L × tile W) ÷ 144
= (12 × 12) ÷ 144
1 ft²
Tile count
ceil(area with waste ÷ tile area)
= ceil(198 ÷ 1)
198 tiles
Grout
((L+W) ÷ (L×W)) × joint × depth ÷ 12 × area × density
= ((12+12) ÷ (12×12)) × 0.125 × 0.375 ÷ 12 × 180 × 115
13.5 lb → 1 bags
How to measure square footage for flooring
Measure each room's length and width in feet and multiply them for the area. A 12 ft × 15 ft room is 12 × 15 = 180 ft². For an L-shaped room, split it into two rectangles and add the areas. Then add a waste allowance for cuts: at the standard 10% for a straight layout that is 180 × 1.10 = 198 ft². If a box covers 20 ft², you need 198 ÷ 20 = 9.9 → 10 boxes. The calculator runs this same math and shows every step.
Flooring waste factor by layout pattern
| Pattern | Typical waste |
|---|---|
| Straight / grid | 10% |
| Diagonal (45°) | 15% |
| Herringbone / chevron | 20% |
| Brick / offset | 10–12% |
Boxes needed by room size (20 ft² per box, 10% waste)
| Room size | Area | With 10% waste | Boxes (20 ft²) |
|---|---|---|---|
| 10 × 10 ft | 100 ft² | 110 ft² | 6 |
| 12 × 12 ft | 144 ft² | 158 ft² | 8 |
| 12 × 15 ft | 180 ft² | 198 ft² | 10 |
| 15 × 20 ft | 300 ft² | 330 ft² | 17 |
| 20 × 25 ft | 500 ft² | 550 ft² | 28 |
How grout coverage is calculated
Grout fills the joints between tiles, so the amount depends on tile size, joint width and tile depth. Smaller tiles have more joint per square foot and use more grout. We use the standard coverage equation and a representative grout density, then round up to whole bags. Because grout yield varies by product, treat the result as an estimate and confirm it against the coverage chart on the bag.
Common flooring estimating mistakes
- •Applying a flat 10% to every job. Diagonal and herringbone layouts waste far more — match the waste factor to your pattern.
- •Buying boxes in batches. Order all boxes at once so they share a dye lot — later boxes can differ in shade.
- •Throwing away the offcuts. Keep the leftover as attic stock for future repairs; matching boards or tiles later is hard.
- •Forgetting underlayment and thin-set. They are separate purchases sized from the floor area, not the box count.
Frequently asked questions
How many 12×12 tiles do I need for 100 square feet?+
A 12×12 inch tile covers exactly 1 ft². For 100 ft² with 10% waste you need 110 tiles. Always round up and buy from one dye lot.
How much waste should I add for a diagonal tile pattern?+
Add about 15% for a diagonal (45°) layout versus 10% for a straight grid, because angled cuts at the perimeter waste more tile. Herringbone runs about 20%.
How many boxes of flooring do I need?+
Measure your room area, add a waste allowance for cuts (10% for a straight layout), then divide by the coverage per box and round up. For 180 ft² with 10% waste and 20 ft² per box, that is 10 boxes.
How much waste should I add for flooring?+
Use a pattern-aware factor: about 10% for a straight grid, 15% for a diagonal layout and 20% for herringbone. Add more for complex rooms with many cuts.
How much extra flooring should I keep as attic stock?+
Keep all the leftover from your waste allowance. Future repair boards or tiles may not match the dye lot, so attic stock is your best match.
Methodology & sources
Area is summed across every room with full precision. Waste follows the chosen pattern and is overridable. Box and tile counts divide the waste-adjusted area by the coverage per box or per tile and round up, with the leftover reported as attic stock. Grout, thin-set and underlayment yields vary by product — confirm before ordering.
- TCNA Handbook for Ceramic, Glass, and Stone Tile Installation + flooring manufacturer installation guidelines — verified June 28, 2026
- Custom Building Products grout coverage data (Polyblend / Prism) — verified June 28, 2026
- Custom Building Products VersaBond thin-set mortar coverage chart — verified June 28, 2026
- Roberts / QEP underlayment product coverage data — verified June 28, 2026
Last reviewed June 28, 2026. Estimates are indicative — verify against current product specs and local requirements before ordering.
We're committed to keeping these tools accurate and improving them over time. If you'd like to contribute to their accuracy, or you run into any issues or errors, please email us at info@tradesppl.com.