Tile & Grout Calculator
Adjust the parameters below to compute materials and estimate project costs.
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Breakdown Details
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Guidelines & Field Recommendations
• Sanded Grout: For joint gaps 1/8" or wider to prevent shrinkage cracks.
• Unsanded Grout: For joints under 1/8" (such as 1/16" or rectified tile).
Calculation Formulas & Steps
Tiles = Area (sq in) ÷ Tile Area (sq in) × 1.10 (waste). Mortar (thinset) averages 1 bag (50lb) per 50 sq ft.
Worked Example (Step-by-Step Math)
Multiply length by width.
12 ft × 10 ft = 120 sq ft = 17,280 sq inDivide area by single tile area (12x12 = 144 sq in). Add 10% cutting waste.
Tiles = (17,280 ÷ 144) × 1.10 = 132 tilesThinset mortar averages 50 sq ft per 50lb bag.
Mortar Bags = 120 sq ft ÷ 50 = 2.4 ≈ 3 bagsGrout Selection Chart
Appropriate grout type based on joint width.
| Project Condition | Reference Metric |
|---|---|
| Sanded Grout | Use for joint gaps 1/8" or wider (prevent shrinkage cracks) |
| Un-sanded Grout | Use for joint gaps under 1/8" (avoid scratching polished surfaces) |
Critical Mistakes to Avoid
- !Mistake 1: Not using tile spacers, resulting in uneven grout lines.
- !Mistake 2: Laying tiles on a flexible subfloor without cement backer board, leading to cracked tiles.
Frequently Asked Questions
When should I use sanded vs unsanded grout based on joint width?
Use sanded grout for joint widths of 1/8 inch or wider. The sand grains act as fillers to support the joint and prevent cracks during shrinking. Use unsanded grout for thin joints under 1/8 inch or on scratch-sensitive tiles like polished marble.
What is the thinset mortar coverage per 50 lb bag of thinset?
A standard 50 lb bag of thinset mortar covers approximately 50 to 60 square feet when applied with a 1/4" x 1/4" notched trowel. For larger tiles requiring a 1/2" x 1/2" trowel, coverage drops to 30 to 40 square feet per bag.
What notched trowel size do I need for laying 12x12 tile?
For standard 12x12 inch floor tiles, use a square-notched trowel measuring 1/4" x 3/8" or 1/2" x 1/2". Larger tiles require deeper mortar notches to ensure full thinset coverage.
How much grout do I need to buy for subway tile?
Subway tiles (3"x6") have a high density of grout lines. For 100 sq ft of subway tile with 1/16" joints, you will need approximately 8-10 lbs of dry grout mix, whereas standard 12x12 tiles need only 3-4 lbs.
Does tile grout need to be sealed and how often?
Yes, cement-based grouts are porous and absorb water, dirt, and mildew. Apply a penetrating grout sealer 48 hours after grouting, and re-apply once a year.
How much tile cutting waste should I buy?
For standard straight grid layouts, add a 10% waste buffer. If laying tiles diagonally or in a herringbone pattern, increase it to 15-20%.
What is cement backer board and why is it used under tile?
A rigid cement sheet screwed to subfloors or wall studs that provides a waterproof substrate for mortar and tile, preventing structural flexing.
Complete Tools Checklist
- Wet Tile Saw
- Notched Trowel
- Grout Float
- Spacers
- Sponge & Bucket