Grout Calculator
Calculate how many 25-lb bags of tile grout you need from your room's area and grout's typical 150 sq ft per bag coverage, plus total cost.
How this calculator works
This calculator divides your tiled area by grout’s typical coverage rate — about 150 square feet per 25-lb bag for a standard 12x12 in tile with a 1/8 in joint — to estimate how many bags to buy.
Formula: Bags = Room area (sq ft) ÷ 150 sq ft per bag.
Worked example
A room 10 ft long x 8 ft wide (80 sq ft):
- Area: 10 x 8 = 80 sq ft
- Bags: 80 ÷ 150 ≈ 0.5333 → 0.53 bags
- At $18/bag, that’s 0.5333 × 18 ≈ $9.60.
Coverage reference
| Room area | Bags needed (150 sq ft/bag) |
|---|---|
| 20 sq ft | 0.13 bags |
| 80 sq ft | 0.53 bags |
| 320 sq ft | 2.13 bags |
How to measure your tiled area
Measure the length and width of the tiled floor or wall in feet, not the room’s full footprint if only part of it is tiled. Then check the coverage chart printed on your specific grout bag against your actual tile size and joint width, since those two factors move the real coverage rate more than any other variable.
Frequently asked questions
How much coverage does one bag of grout give?
This calculator uses 150 sq ft per 25-lb bag, which assumes a 12x12 in tile with a 1/8 in joint width — a common floor-tile setup. That figure shifts a lot with different tile sizes and joint widths, so treat it as a solid starting estimate rather than an exact figure for every job.
How does joint width change how much grout I need?
Joint width is the single biggest variable in grout coverage. Widening a joint from 1/8 in to 1/4 in roughly doubles the grout volume per square foot, since grout fills the joint's cross-section, not the tile face. Always check your tile spacer size against the coverage chart on the actual bag before ordering.
Does tile size affect grout quantity?
Yes, significantly. Smaller tiles (like 4x4 in mosaic) have far more linear feet of joint per square foot of floor than large-format tile (18x18 in or bigger), so small tile can need two to three times more grout for the same area, even at the same joint width.
Sanded or unsanded grout — does it change the bag count?
Coverage per bag is similar between sanded and unsanded formulas at the same joint width, so this calculator's yield applies either way. The real deciding factor is joint width: unsanded grout is typically used for joints under 1/8 in, and sanded grout for 1/8 in and wider.
Why isn't a waste allowance offered for grout?
Grout is mixed in small batches and any excess in an opened bag doesn't spoil quickly, so most installers just round up to the next whole bag rather than adding a waste percentage on top. Buying one extra bag from the same production lot is cheap insurance against running short mid-job.
Estimates only. Verify quantities with your supplier before purchasing.