Grout Calculator
Calculate exactly how much grout you need for your tiling project. Enter tile length, width, and thickness, joint width, and total area to tile. Choose between sanded, unsanded, and epoxy grout. Get the precise grout weight needed with and without waste, number of tiles required, total linear feet of joints, and cost estimate. The calculator suggests the most economical box size (1-, 2-, 5-, 10-, 25-, or 50-lb) and how many boxes to buy. Avoid running short or wasting money on excess grout.
Length of one tile
Width of one tile
1/8 inch is standard for most tiles
Total square footage of the tiling surface
Extra for spillage, mixing errors, and touch-ups
How do I calculate how much grout I need?
Grout volume depends on tile size, joint width, and tile thickness. Formula: Grout Volume (cu in per sq ft) = (Joint Width × Tile Thickness × (Tile Length + Tile Width)) ÷ (Tile Length × Tile Width) × 144. Then convert to pounds: sanded grout ≈ 90-100 cu in per lb, unsanded ≈ 120-140 cu in per lb. For 12×12 inch tiles with 1/8 inch joints and 1/4 inch thickness: grout ≈ 0.33 lbs per sq ft × 100 sq ft = 33 lbs. Using 10-lb boxes: buy 4 boxes.
How many square feet does a 10 lb bag of grout cover?
Coverage varies by tile size: 12×12 inch tiles with 1/8 inch joints: about 25-30 sq ft per 10-lb bag. 6×6 inch tiles: about 15-20 sq ft. 18×18 inch tiles: about 35-40 sq ft. Mosaic tiles (2×2): only 8-12 sq ft. Subway tiles (3×6): about 18-22 sq ft. Larger tiles cover more because there are fewer linear feet of joints per square foot. Always check the manufacturer's coverage chart on the grout box for exact numbers.
What is the difference between sanded and unsanded grout?
Sanded grout contains fine sand and is used for joints wider than 1/8 inch. It is stronger, less prone to cracking, and better for floor tiles. Unsanded grout has no sand and is used for joints 1/8 inch or narrower. It is smoother and works better for polished stone and wall tiles where scratching is a concern. Epoxy grout is the strongest and most stain-resistant but harder to work with. For showers and wet areas, epoxy grout is recommended for water resistance and mold prevention.
How do I avoid common grout estimating mistakes?
Common mistakes: Forgetting that mosaic tiles need much more grout than large format tiles. Not accounting for waste (always add 10-15%). Using the wrong grout type for joint width. Not considering that thicker tiles use more grout. Forgetting to grout the same color batch throughout — mix multiple boxes together dry before adding water. Always buy one extra box beyond your estimate — color matching later is nearly impossible. Store extra grout in a sealed container with desiccant for future touch-ups.