Grout Calculator: How Much Grout Do I Need?
Use this tile grout calculator to find out how many pounds of grout you need and how many bags to buy. Enter the area, tile size, thickness and joint width. A 10% waste allowance is included.
By Troopus · Updated: October 28, 2026
- Pounds and bags
- 10% waste built in
- Live result
- 100% private
Tile grout calculator
More options
Estimate for information only. Actual use depends on the product, joint depth, tile edges and how you work. Check the coverage on your grout bag and buy a little extra.
How much grout do I need with this grout calculator?
For 100 sq ft of 12 x 12 inch tile that is 3/8 inch thick with 1/8 inch joints, this grout calculator estimates about 6.5 lb, or 7.2 lb with a 10% waste allowance. Smaller tiles and wider joints need much more, because there is more joint length to fill.
A grout calculator estimates the weight of grout needed to fill the joints between tiles, from the area, tile size, tile thickness and joint width.
Enter the area (or switch to room length and width), the tile length, width and thickness, and the joint width. The result updates as you type and shows pounds of grout plus the number of 8 lb, 10 lb and 25 lb bags to buy. The default 10% waste covers spills, cleanup and mixing leftovers. You can change it under More options.
| Tile (L x W x thickness) | Joint | Grout needed |
|---|---|---|
| 24 x 24 x 3/8 in | 3/16 in | 5.4 lb |
| 12 x 24 x 3/8 in | 1/8 in | 5.4 lb |
| 12 x 12 x 3/8 in | 1/8 in | 7.2 lb |
| 3 x 6 x 1/4 in | 1/16 in | 7.2 lb |
| 4 x 4 x 5/16 in | 3/16 in | 26.9 lb |
| 2 x 2 x 1/4 in | 1/8 in | 28.6 lb |
Bag sizes vary by product, so check the label. LATICRETE, for example, lists 25 lb bags for several of its cement grouts and an 8 lb bag for one base powder.
What formula does a grout coverage calculator use?
Grout (lb) = area x 144 x (L + W) / (L x W) x joint width x tile thickness / 1,728 x density x (1 + waste). Tile and joint sizes are in inches, area is in square feet, and density is in pounds per cubic foot. This calculator uses 100 lb per cubic foot unless you change it.
The idea is to find the volume of the joints and turn it into weight:
- Joint length per square foot of floor = 144 x (L + W) / (L x W) inches. Each tile has half of its four edges in its own share of the joints, which is why the sum L + W appears.
- Joint volume per square foot = joint length x joint width x joint depth, in cubic inches. Depth is assumed to equal the tile thickness.
- Divide by 1,728 to get cubic feet, then multiply by the grout density to get pounds.
- Multiply by the area, then add the waste allowance.
Worked example, 12 x 12 x 3/8 in tile with 1/8 in joints: 144 x 24 / 144 = 24 inches of joint per sq ft; 24 x 0.125 x 0.375 = 1.125 cu in; 1.125 / 1,728 x 100 = 0.065 lb per sq ft. For 100 sq ft that is 6.51 lb, and 7.16 lb with 10% waste.
The geometric method is the one manufacturers use for coverage: LATICRETE says coverage depends on tile size, tile thickness and joint width, and manufacturers publish their own coverage figures, each with its own density factor. Density is the weakest part of any generic formula. Published formulas and calculators use roughly 95 to 112 lb per cubic foot, so this tool lets you edit it.
How many bags of grout do I need?
Divide the pounds of grout needed by the bag size and round up. For 7.2 lb you need one bag of any common size, for example an 8 lb or 25 lb bag. The calculator shows 8 lb, 10 lb and 25 lb bag counts together, so you can match what your store sells.
Rounding up matters more than it looks, because grout is mixed in small batches and color varies between production lots. If your job needs a number just above a bag size, buy the extra bag and keep the leftover for repairs. Pre-mixed grout and epoxy are sold by volume, not weight, so use your product label if it is not a powder.
Should I add extra grout for waste?
Yes. Add about 10% for spills, cleanup and mixing waste, and more for rough or uneven tile. LATICRETE suggests at least 10% extra, and adds 10% to 15% more for unglazed quarry tile. This grout calculator uses 10% by default and lets you change it.
Waste is higher when tile edges are rough, when the substrate is uneven, when you grout in small sections or when you are new to the job. Joint depth also matters: if your tile has a recessed back or you deepen the joints, actual use goes up. Pro installers often compare the result with the coverage chart on the bag. If the chart says more, trust the chart.
Related: for floor area you can use the percentage calculator to check waste math.
Why does smaller tile need more grout?
Smaller tile has more joint length per square foot, so it needs more grout. A 2 x 2 inch tile has 72 inches of joint per square foot, six times the 12 inches of a 24 x 24 inch tile. Wider and deeper joints raise the amount in direct proportion.
Joint width and thickness both multiply the result. Doubling the joint width doubles the grout. Use your tile spacers, not guesses, to measure the real width. For large format tile with narrow joints the quantity is small, but cleanup waste is a larger share of it, so keep the waste allowance.
Frequently asked questions
How do I calculate how much grout I need?
Find the joint volume per square foot from tile length, width, thickness and joint width, convert it to pounds using grout density, multiply by the area and add about 10% for waste. The calculator above does these steps live.
How much grout do I need for 100 square feet?
For 12 x 12 inch tile that is 3/8 inch thick with 1/8 inch joints, about 6.5 lb, or 7.2 lb with 10% waste. Small mosaic tile or wide joints can need several times more.
How many square feet does a 25 lb bag of grout cover?
It depends on tile size, joint width and depth, and the product. Use this calculator for the pounds you need, then compare with the coverage printed on your bag, since manufacturers publish their own charts.
How much grout do I need for a shower or backsplash?
Measure the tiled area in square feet and enter the same tile and joint sizes. Backsplash jobs are small, so a single small bag is often enough, but small tile and wide joints can raise the need.
Do I need more grout for wide joints?
Yes. Grout use rises in direct proportion to joint width and joint depth. Doubling the joint width doubles the amount of grout, which is why wide joints and thick tile need much more.
What tile thickness should I enter?
Enter the real thickness of your tile, such as 1/4 or 3/8 inch. This tool assumes the joint is filled to the full thickness. If your joints are shallower, you will use less.
Is sanded or unsanded grout calculated differently?
The geometry is the same. The weight per cubic foot can differ between products, so you can change the grout density under More options if your product data sheet lists it.
Why does the result differ from the bag coverage?
Manufacturer charts reflect their own product density, typical joint depth and normal job waste. This tool shows a clear estimate with the numbers you enter. When in doubt, follow the bag and buy one extra.