🧱 Grout Calculator
Enter your tiled area, tile size, thickness, and joint width to see the pounds of grout and how many 25-pound bags to buy — using the standard tile-industry coverage formula.
Planning estimate — always cross-check the coverage chart on the grout bag.
🧮 Estimate Your Grout
🧱 Grout you'll need
How much grout will the joints take?
Grout quantity isn't about the tile — it's about the gaps between the tiles. A floor of tiny mosaics has far more joint to fill than the same floor in large-format tile, and every extra millimetre of joint width or tile thickness adds up. Guessing usually means a second trip to the store mid-job.
This calculator applies the standard tile-industry coverage formula — factoring in tile size, joint width, and thickness — to turn your area into pounds of grout and whole 25-pound bags. Read exactly how the math works in the FAQ below.
❓ Frequently Asked Questions
What formula does this grout calculator use?
It uses the standard tile-industry coverage formula. With every dimension in inches and the area in square feet: grout pounds per square foot = ((tile length + tile width) ÷ (tile length × tile width)) × joint width × tile thickness × K. The constant K = 8.75 converts the joint-volume fraction into pounds, and comes from 144 in²/ft² × (105 lb/ft³ ÷ 1728 in³/ft³) — that is, an assumed cured grout density of about 105 lb/ft³. Multiply the pounds-per-square-foot by your total area for the pounds needed.
Why do smaller tiles and wider joints need more grout?
Grout fills the gaps between tiles, so the more linear feet of joint per square foot of floor, the more grout you use. Small mosaics have far more joint per area than large-format tile, and wider or deeper joints hold more grout in each gap. That's exactly why tile size, joint width, and tile thickness all appear in the formula.
How many pounds are in a bag of grout?
Grout is commonly sold in 25-pound bags, which is what this calculator assumes when it tells you how many bags to buy. Some brands also sell 10- or 8-pound bags for small jobs. It always rounds up to whole bags and it's wise to keep a little extra for mixing loss and future repairs.
Is the estimate exact?
No — it's a planning estimate. Actual coverage varies with grout brand and density, how full you pack the joints, tile surface texture, and waste from mixing. Trowel technique matters too. Always cross-check against the coverage chart printed on the grout bag before you buy, and round up rather than down.