Grout Calculator Tile Stone. Grout calculations depend on tile size and joint width. Formula: Pounds per Sq Ft equals (Tile Length plus Width divided by Length times Width) times Joint Width times Depth times 1.8. Example 12×12 tile, 1/4 inch joint, 3/8 inch deep: (12 plus 12 divided by 144) times 0.25 times 0.375 times 1.8 equals 0.28 pounds per sq ft. For 100 sq ft: 28 pounds needed. One 25-pound bag covers 75-150 sq ft depending on tile size and joint. Grout types: Sanded grout for joints 1/8 inch and wider, provides strength, slightly coarse. Unsanded grout for joints under 1/8 inch, smooth, won't scratch polished surfaces like marble. Epoxy grout stain-proof waterproof, expensive, difficult to apply, best for countertops and showers. Choose based on joint size and tile type. Joint width affects coverage dramatically: 1/16 inch joints use half the grout of 1/8 inch. 1/4 inch joints use double 1/8 inch joints. Wider joints traditional rustic, narrower joints modern. Rectified tiles allow 1/16 inch joints, non-rectified need 1/8 inch minimum. Cost considerations: Sanded grout 10-15 per 25-pound bag. Unsanded 12-18 per bag. Epoxy 60-120 per bag. Estimate 2-4 bags per 100 sq ft average tile. Labor included in tile installation typically. DIY material cost minimal 50-100 for whole-house project. Tile size affects grout amount: Small tiles (4×4 or mosaic) have more grout lines, use 3-5 pounds per 100 sq ft. Medium tiles (12×12) standard 2-3 pounds per 100 sq ft. Large tiles (18×18 or 24×24) fewer grout lines, 1-2 pounds per 100 sq ft. More grout needed for smaller tiles with more joints. Application process: Mix grout to thick paste consistency. Apply with rubber float diagonal to joints. Pack joints completely. Scrape excess at 45-degree angle. Let haze 15-30 minutes. Sponge clean with damp (not wet) sponge changing water frequently. Buff with dry cloth after drying. Wait 48-72 hours before sealing. Common mistakes: Mixing too much grout, sets in 30-60 minutes, discard unused. Cleaning with too much water, weakens grout. Not packing joints fully leaves voids. Grouting before thinset fully cured 24-48 hours. Using sanded on polished stone scratches surface. Applying sealer too soon prevents proper curing. Walking on floor before grout cures damages joints. Pro tips: Add grout admix instead of water increases strength and flexibility. Work in small sections 3-4 sq ft at a time. Clean sponge often, multiple rinses needed. Wear knee pads, grouting hard on knees. Mix to peanut butter consistency. Let slake 10 minutes before final mixing. Use grout bag for very small joints like penny tile. Color and sealing: Grout colors white, gray, beige, brown, black, match or contrast tile. Test sample in corner before full application. Color sealer can change color later if desired. Penetrating sealer recommended for non-epoxy grout, reapply yearly or every 2 years depending on traffic. Grout turns darker when wet is normal. Sealing prevents staining and moisture damage. Grout removal and repair: Remove old grout with grout saw or rotary tool, tedious. Avoid damaging tile edges. Vacuum debris. Apply new grout same process as initial installation. Color needs to match, difficult, test first. Sometimes easier to regrout entire area for uniform color. Professional regrouting 3-7 per sq ft. Epoxy grout considerations: Extremely strong and stain-proof, ideal for kitchens and countertops. Difficult to apply, sets fast, very sticky, requires skill. Costs 3-4 times sanded grout. Cannot be sealed, doesn't need sealing. Cleaning requires specific solvents. Hire professional for epoxy grouting unless very experienced. Grout vs caulk: Use caulk not grout for corners where walls meet, floor meets tub, any expansion joint. Grout rigid, cracks at movement joints. Caulk flexible, accommodates movement. Match caulk color to grout. Use latex or silicone caulk, never grout where movement occurs. FAQ: How much grout for 100 sq ft? Depends on tile size, typically 2-4 pounds for standard 12×12 tile with 1/4 inch joints. Sanded or unsanded? Sanded for joints 1/8 inch and wider. Unsanded for smaller joints and polished stone. Must I seal grout? Yes for sanded and unsanded grout prevents stains. Epoxy doesn't need sealing. Reapply every 1-2 years. Why is grout cracking? Thinset not fully cured when grouted, joints too narrow, no expansion joints, substrate movement, poor mixing, cheap grout. Can I change grout color? Yes with grout stain or color sealer, or remove and replace. How long before showering? 48-72 hours lets grout cure properly.