Grout Calculator: How Much Grout Do I Need?

How to measure for grout

Methods for taking the four measurements:

1. Area to grout. Multiply length by width for a floor, or width by tiled height for a wall or backsplash. Split an L-shaped room into rectangles; our square footage calculator adds them up.
2. Tile length and width. Read them from the box or measure a tile, in inches.
3. Tile thickness. Measure it with a tape at a cut edge, or take it from the box, and type it as a decimal: 1/4 in = 0.25, 3/8 in = 0.375, 1/2 in = 0.5. It's used as the joint depth.
4. Joint width. Read it from your spacers, from 1/16 to 1/2 in.

Then pick a 25 lb or 10 lb bag and the extra (10% to start).

Quick answers: grout for a backsplash, a shower, and floors

4.3 lb of grout for a 30 sq ft backsplash of 3 x 6 in subway tile, and 7.2 lb for a 10 x 10 ft floor of 12 x 12 in tile. Each row is an example size worked with the calculator's formula, with 1/8 in joints filled to the tile's full depth and 10% extra. For walls, the area is the width times the height you tile:

Any amount up to 10 lb is one 10 lb bag, and up to 25 lb one 25 lb bag: the 300 sq ft floor takes 4 bags of 25 lb in 2 x 2 in mosaic (85.8 lb) but 1 bag in 12 x 24 in tile (16.1 lb). With 1/4 in joints, each figure doubles. For a shower, add the walls and the floor: 7.7 lb for subway tile walls plus 2.6 lb for a mosaic floor is 10.3 lb.

Grout per 100 sq ft by tile size and joint width

Pounds per 100 sq ft, before extra, computed with the formula above:

For 200 sq ft of 12 x 24 in tile with 1/8 in joints, that's 9.8 lb, or 10.7 lb with 10% extra: one 25 lb bag, which covers about 513 sq ft. Unsanded grout stops at 1/8 in. Many sanded grouts start at 1/8 in (Keracolor S, Polyblend Plus Sanded), but LATICRETE 1500 Sanded and Ultracolor Plus FA go down to 1/16 in.

How many square feet a 25 lb bag of grout covers

384 sq ft of 12 x 12 x 3/8 in tile with 1/8 in joints, or 96 sq ft of 2 x 2 in mosaic. Square feet per 25 lb bag, before extra, by the same formula; the calculator prints this figure under each result:

For a 10 lb bag, multiply by 0.4: 154 sq ft of 12 x 12 in tile with 1/8 in joints. For 2 x 2 in mosaic with 1/8 in joints, the Keracolor S, Ultracolor Plus FA, and Polyblend Plus Sanded charts list 93 to 97 sq ft per 25 lb. For tile 6 x 6 in and larger, the two MAPEI charts stay within 2% of the table at joints up to 1/4 in, while the Polyblend Plus Sanded chart at 1/8 in joints calls for 8% to 12% more grout (348 sq ft instead of 384 for 12 x 12 in tile).

Why the bag chart may differ

Coverage varies by product: MAPEI's calculator works from "the actual volume to be filled and the product density." Each maker's chart for 12 x 12 x 3/8 in tile with 1/8 in joints:

• Close match: for tile 6 in and up with joints to 1/4 in, the Keracolor S and Ultracolor Plus FA charts stay within 2% of the formula.
• More grout: Polyblend Plus Sanded needs about 10% more than the calculator shows (384 ÷ 348).
• Unsanded varies both ways: Polyblend Plus Non-Sanded needs about 5% more; Keracolor U about 27% less.
• Mosaics: charts disagree even within one brand. For 1 x 1 in tile, the formula gives 9.6 sq ft per 25 lb at 5/8 in joints (Keracolor S chart: 7) and 8.0 at 3/4 in (Ultracolor Plus FA chart: 9).

Joints vary too: CUSTOM's coverage bulletin notes that 1/8 in joints off by 1/32 in change the grout needed by 25% (5/32 ÷ 1/8 = 1.25). These are makers' published numbers, not a ranking; compare this estimate with your bag's chart and plan on the larger amount.

Epoxy and premixed grout coverage

187 sq ft of 12 x 12 x 3/8 in tile with 1/8 in joints per 9.5 lb unit of CUSTOM's CEG-Lite epoxy grout, and 199 sq ft per gallon of its premixed Fusion Pro: about half of what a 25 lb bag of cement grout covers by the formula (384). These grouts come in units and pails, not 25 lb bags, so go by the product's chart instead of the calculator's pounds. From CUSTOM's charts:

Divide the area, with extra, by the chart figure and round up: 100 sq ft of 12 x 12 in tile with 1/8 in joints and 10% extra is 110 ÷ 187 = 0.59, so 1 unit of CEG-Lite, and CUSTOM's 19 lb unit covers double. Full units of epoxy must be mixed and used all at one time, so the excess is lost, CUSTOM's coverage bulletin warns, while excess Fusion Pro can go back in the pail. LATICRETE lists a yield of 0.8 gal for a full unit of SPECTRALOCK PRO Premium epoxy grout (0.2 gal mini, 3.2 gal commercial), for joints from 1/16 to 1/2 in. At the joint volume this formula uses, 1.125 cu in per sq ft for 12 x 12 x 3/8 in tile with 1/8 in joints, 0.8 gal (184.8 cu in) fills about 164 sq ft. LATICRETE asks for at least 3/4 of the Part C powder and notes that less powder lowers coverage. MAPEI's Kerapoxy CQ epoxy grout takes joints from 1/16 to 3/8 in.

Sanded or unsanded grout?

Choose by joint width first. Each maker's data sheet gives the range:

MAPEI's Keracolor U sheet rules out joints wider than 1/8 in, and its Keracolor S sheet rules out joints under 1/8 in. LATICRETE advises unsanded grout for soft or polished marble, other soft stone, some polished stone, and soft glazed tile with joints of 1/8 in or less, and sanded grout for other tile and stone with joints from 1/16 to 1/2 in. The type doesn't change the calculator's math, only which chart to check.

Tips and common mistakes

• Buy 5% to 10% extra. MAPEI recommends that much overage, since actual coverage may vary with job conditions and application methods.
• Fill the joints. CUSTOM's tip is to fill joints at least 2/3 full; with epoxy or single-component grout, it lets the setting material fill the lower third. If you'll do that, enter two-thirds of the tile thickness (0.25 in for 3/8 in tile).
• Check the joint you actually get. Measure a few joints once the tile is set; 1/32 in wider than 1/8 in takes 25% more grout.
• Large tile. See the grout joints section of our tile calculator guide for joint-width rules.
• Other grout types. For epoxy, urethane, or premixed grout, go by that product's coverage chart.