Grout Calculator
Calculate how much grout you need for your tile project based on tile size, joint width, and area. See also our Tile Calculator, Mortar Calculator, and Flooring Calculator.
How to Use the Grout Calculator
Enter your tile dimensions (width and length in inches), select the grout joint width, enter the joint depth (typically equal to tile thickness minus 1/16 inch), and input the total area to be grouted in square feet. The calculator determines the total pounds of grout needed, number of 25-pound bags to purchase, coverage per bag, and mixing water required. Always buy one extra bag for waste and touch-ups.
Joint depth is important for grout durability. The grout should fill at least 2/3 of the tile thickness. For standard 3/8-inch thick wall tiles, use 1/4-inch joint depth. For 1/2-inch thick floor tiles, use 3/8-inch depth. Deeper joints use more grout but create a stronger, more durable installation that resists cracking and wear over time.
Formula
Joint length per sq in = (Tile W + Tile L) / (Tile W x Tile L)
Grout volume per sq ft = Joint length x Joint W x Joint D x 144
Grout weight = Volume x Density (100 lbs/cu ft)
Bags (25 lb) = Total weight / 25 (rounded up)
Water = Weight / 6.25 x 0.25 gallons
Example Calculation
Tile: 12"x12", 1/8" joints, 1/4" depth, 100 sq ft
Joint length/sq in = (12+12)/(12x12) = 0.167 in/sq in
Grout vol/sq ft = 0.167 x 0.125 x 0.25 x 144 = 0.75 cu in/sq ft
Total volume = 0.75 x 100 = 75 cu in
Weight = 75 x (100/1728) = 4.34 lbs
Bags = 1 bag (25 lb covers ~575 sq ft at this size)
Reference Table: Grout Coverage by Tile Size
| Tile Size | 1/8" Joint | 3/16" Joint | 1/4" Joint |
|---|---|---|---|
| 4" x 4" | 45 sq ft/bag | 30 sq ft/bag | 22 sq ft/bag |
| 6" x 6" | 70 sq ft/bag | 45 sq ft/bag | 35 sq ft/bag |
| 8" x 8" | 95 sq ft/bag | 60 sq ft/bag | 45 sq ft/bag |
| 12" x 12" | 140 sq ft/bag | 95 sq ft/bag | 70 sq ft/bag |
| 12" x 24" | 190 sq ft/bag | 125 sq ft/bag | 95 sq ft/bag |
| 18" x 18" | 210 sq ft/bag | 140 sq ft/bag | 105 sq ft/bag |
| 24" x 24" | 280 sq ft/bag | 190 sq ft/bag | 140 sq ft/bag |
Frequently Asked Questions
What is the difference between sanded and unsanded grout?
Sanded grout contains fine sand particles and is used for joints 1/8 inch and wider. It's stronger and resists cracking in wider joints. Unsanded grout is smooth and used for joints narrower than 1/8 inch, polished stone, and glass tile where sand could scratch the surface. Always match grout type to joint width.
How wide should grout joints be?
Standard ceramic tile uses 1/8 to 3/16 inch joints. Rectified (precision-cut) tile can use 1/16 inch joints. Natural stone typically uses 1/4 to 1/2 inch joints. Larger tiles (12 inch+) generally use narrower joints (1/8 inch) for a cleaner look. Always follow tile manufacturer recommendations.
How long does grout take to dry?
Grout is ready for light foot traffic in 24 hours. Full cure takes 28 days. Avoid heavy traffic, moisture, and cleaning for at least 72 hours. In humid conditions or cold temperatures, allow extra drying time. Seal grout after full cure (28 days) for cement-based grout; epoxy grout does not require sealing.
Should I seal my grout?
Yes, cement-based grout (both sanded and unsanded) should be sealed to prevent staining and moisture absorption. Apply penetrating sealer after 28 days of curing. Reapply annually in wet areas (showers, kitchen backsplash) and every 2-3 years in dry areas. Epoxy grout is naturally stain-resistant and does not need sealing.
How much grout do I mix at once?
Mix only as much grout as you can use in 20-30 minutes (the working time before it begins to set). For most DIY projects, mix 2-3 pounds at a time. For large areas with experienced installers, mix up to half a bag. Never add water to grout that has started to set — discard it and mix a fresh batch.
What causes grout to crack?
Common causes include: too much water in the mix (weakens the grout), joints that are too shallow (less than 2/3 of tile thickness), movement in the substrate (use crack isolation membrane), missing expansion joints at walls and transitions, and applying grout before thinset has fully cured. Proper preparation prevents most grout failures.