Tile jobs fail at the ordering stage more often than the installing stage: not enough tile from the right dye lot, the wrong trowel for the tile size, or a grout run that comes up two pounds short on a Sunday. The calculator below converts your space into tiles, thinset bags, and grout based on tile size and layout pattern, and the sections after it explain the numbers.
Tile Calculator
Grout usage varies with joint width and tile thickness; the estimate assumes a 1/8-3/16 inch joint. Large format tile (>15 inches on any side) needs a 1/2 inch notched trowel and large-format mortar, which is why its thinset count is higher.
The Math & Why Pattern Sets the Waste
Tiles needed = (area × waste factor) ÷ tile area. The waste factor tracks how many perimeter tiles get cut and whether offcuts are reusable: a straight grid in a rectangular room reuses most end cuts (10%), diagonal layouts cut every border tile at 45 degrees (15%), and herringbone cuts everything at the edges with short unusable remainders (20%). Wood-look plank tile in a running bond adds a subtlety: offsets over 33% on long planks can lip because tiles bow slightly in firing, so most manufacturers specify a one-third offset, which also keeps waste near 10%.
Thinset & Grout: Getting the Bags Right
A 50-pound bag of modified thinset covers roughly 60-85 square feet with the 1/4 inch square-notch trowel used for tile up to about 12x12. Any tile over 15 inches on a side is large format: it needs a 1/2 inch notch, a mortar rated LFT (large format tile) that resists slump, and back-buttering, which together drop coverage to 40-50 square feet per bag.
Grout comes down to joint size. At the common 1/8 to 3/16 inch joint, a 25-pound bag handles roughly 300-400 square feet of large tile but as little as 100-150 square feet of small-format tile like subway or mosaic, because small tile has far more linear feet of joint per square foot. Prefer premixed urethane or ready-to-use grout for small jobs; it costs triple per pound and is worth it for zero mixing errors.
What Goes Under Tile
| Location | Correct base | Notes |
|---|---|---|
| Kitchen backsplash | Drywall is fine | Dry area; skim off gloss paint |
| Bathroom floor | Cement board or uncoupling membrane over plywood | Thinset under the board too |
| Shower walls | Cement board + waterproofing, or foam board system | Never green drywall |
| Concrete slab | Direct, with crack-isolation membrane over cracks | Flatten high spots first |
| Heated floors | Uncoupling/heat membrane | Tile is the best flooring over radiant heat |
Flatness is the hidden requirement
Large-format tile needs a floor flat to 1/8 inch over 10 feet, which most subfloors are not. Budget for a bag or two of self-leveling underlayment on any floor tile job. Lippage between big tiles is the most common complaint on DIY installs, and it's a flatness problem, not a skill problem.
What Tile Costs in 2026
| Tile | Material / sq ft | Notes |
|---|---|---|
| Ceramic (basic) | $1-$4 | Walls and light-duty floors |
| Porcelain | $2-$8 | The floor default; harder to cut |
| Wood-look plank porcelain | $3-$9 | One-third offset rule applies |
| Natural stone (marble, travertine) | $6-$25 | Needs sealing; softer than porcelain |
| Mosaic / specialty | $8-$30+ | Sold by the sheet; labor-intensive |
Add thinset ($15-$45/bag), grout ($15-$30), backer board ($12-$18/sheet), and waterproofing for wet areas.
Tiling a bathroom as part of a bigger job? The bathroom remodel timeline shows exactly where tile and its cure times sit in the schedule, and the drywall calculator covers the walls around the wet area.
Frequently Asked Questions
How many 12x24 tiles do I need for 100 square feet?
Each 12x24 tile covers 2 square feet, so 100 square feet is 50 tiles before waste. With a standard 10% waste factor for an offset layout you'd order 55 tiles, or 60 for a herringbone pattern.
How much extra tile should I buy?
10% for straight and offset layouts, 15% for diagonal, and 20% for herringbone. Small rooms with lots of cuts deserve the high end. Always keep a few spares after the job; a matching dye lot won't exist in five years when a tile cracks.
How much does a 50 lb bag of thinset cover?
About 60-85 square feet with a 1/4 inch square-notch trowel for standard tile, and roughly 40-50 square feet with the 1/2 inch notch that large-format tile requires. Buy one bag more than the math says; running out with a wall half-set is not a position you want to be in.
Can you tile over drywall?
In dry areas like a kitchen backsplash, yes, tile bonds fine to painted drywall. In showers and tub surrounds, no; use cement board or a foam backer board with waterproofing. Green moisture-resistant drywall inside a shower is against code in most jurisdictions and fails eventually.
How much does tile installation cost in 2026?
Labor runs $6-$15 per square foot for straightforward floor tile and $10-$25 for showers, patterns, and small-format mosaic. With mid-range porcelain at $2-$8 per square foot for material, a typical 100-square-foot floor lands between $1,000 and $2,300 installed.
Tile Showers and Floors, Done Right in Will County
Rehab Addicts installs tile floors, showers, and backsplashes as part of bathroom and kitchen remodels across Joliet, Shorewood, and Will County, IL. Free estimates.
