Grout Calculator
This free grout calculator tells you how much grout to buy for your tiling project. Enter your tiled area, tile size, grout joint width and depth — it instantly estimates the grout weight in pounds (with your waste allowance) and how many 10-lb and 25-lb bags you need.
Enter your numbers
Results update as you type.
Your results
Enter your tile and joint dimensions to see the estimate.
How to use this calculator
Measure the tiled area in square feet — length times width of each tiled surface, added together. Then enter your tile length and width in inches (a "12×12" floor tile is 12 by 12 inches). The grout joint width is the gap you leave between tiles — 1/8 in (0.125) is typical for walls, 3/16 in (0.1875) or 1/4 in (0.25) for floors. The joint depth is roughly two-thirds of the tile thickness; when in doubt, use the full tile thickness for a safe estimate.
Finally, set a waste allowance — 10% is the standard recommendation for spill, overfilling, and joints that end up deeper than planned. The calculator updates instantly as you type and rounds the bag counts up, since you can only buy whole bags.
How it works
Grout only goes into the joints between tiles, so the estimate starts from the total joint volume. Step by step:
1. Tile count. Convert the area to square inches (× 144) and divide by the face area of one tile:
ntiles = area (sq ft) × 144 ÷ (tile length × tile width)
2. Total joint length. Every interior joint is shared by two tiles, so on average each tile contributes half its perimeter:
joint length = ntiles × (tile length + tile width) (in inches)
3. Joint volume. Treat each joint as a rectangular channel:
volume = joint length × joint width × joint depth (in cubic inches)
4. Weight. Multiply by the bulk density of sanded grout, taken here as ≈ 110 lb/ft³ = 0.0637 lb/in³, then add your waste allowance:
weight = volume × 0.0637 × (1 + waste ÷ 100)
Worked example — 100 sq ft, 12×12 in tiles, 0.25 in joints, 0.25 in deep, no waste: n = 100, joint length = 2,400 in, volume = 150 in³, weight = 150 × 0.0637 ≈ 9.55 lb.
Estimate, not an exact figure. The density assumption is for standard sanded grout; unsanded grout is slightly lighter, and actual joints vary in depth. Results are planning estimates — confirm with your tile supplier before ordering.
Frequently asked questions
How much grout do I need for 100 sq ft of tile?
It depends on your tile size and joint width, but as an example: 100 sq ft of 12×12 in tiles with 0.25 in joints that are 0.25 in deep needs about 9.55 lb of grout before waste. With the recommended 10% waste allowance that's about 10.5 lb — so one 10-lb bag covers it, and two if you want a spare. Enter your own numbers in the calculator above for an exact count.
How is grout coverage calculated?
Grout fills the joints between tiles, so you need the total joint volume: first the number of tiles (area in sq in ÷ tile face area), then the total joint length — each tile contributes half its perimeter on average, so joint length = tiles × (tile length + tile width). Multiply by the joint width and joint depth to get the grout volume in cubic inches, then convert to pounds using the grout's bulk density (about 0.0637 lb/in³ for sanded grout). The calculator on this page does all of this for you.
Should I use sanded or unsanded grout?
Use sanded grout for joints 1/8 in (0.125 in) or wider — the sand keeps wide joints from shrinking and cracking. Use unsanded grout for narrower joints (under 1/8 in), where sand particles would be too coarse. The weight estimate on this page assumes sanded grout at about 110 lb/ft³; unsanded grout is slightly lighter, so treat the result as an estimate and round up.
How many pounds of grout do I need per square foot?
There is no single answer — it scales with joint width and tile size. As a reference, 12×12 in tiles with 0.25 in joints need about 0.096 lb of grout per square foot, while 4×4 in tiles with the same joints need roughly three times that, about 0.29 lb per square foot, because smaller tiles mean more joints. Add 10% waste on top and convert to bags: ceil(total ÷ bag size).