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Reviewed · Prices checked October 2026 · How we calculate

Grout Calculator: How Much Grout Do I Need?

Enter the area, your tile's size and thickness, and the joint width. You get the pounds of grout to fill the joints, the bags to buy, and whether to get sanded or unsanded.

Inputs

Units
sq ft
in
in
Joint width

The spacer size. Under 1/8 in takes unsanded grout; 1/8 in and wider, sanded.

Tile thickness

Shopping list

Updates as you type
1bag

of sanded grout (25 lb) for 100 sq ft of 12 × 12 in tile with 1/8 in joints: about 7.6 lb

  • 1 bag of sanded grout (25 lb)$22–$33
    About 7.6 lb to fill the joints.

    Typical price (estimate, checked Oct 2026): $22.00–$33.00 per 25 lb bag of sanded grout

    1 bag × $22.00–$33.00 = $22–$33Estimate
Grout total (estimated)$22–$33
Checked Oct 2026
Show the math
100 sq ft × 144 × (12 + 12) ÷ (12 × 12) × 1/8 in × 3/8 in × 0.0672 lb per cu in = 7.6 lb7.6 lb ÷ 25 lb per bag = 0.30 → 1 bag

Your prices are saved on this device only.

How it works

The formula

lb = area × 144 × (L + W) ÷ (L × W) × joint × thickness × 0.0672
bags = lb ÷ bag weight, rounded up

Assumptions

  • The formula is the joint volume (length of joint per sq ft × joint width × tile depth) times the weight of grout, about 0.0672 lb per cubic inch for sanded grout. It fills every joint to the full tile depth, so it comes out a little above Custom Building Products' coverage chart (see the table below): a small margin for the sponge and the bucket.
  • Joints under 1/8 in take unsanded grout, which comes in 10 lb bags; 1/8 in and wider take sanded, in 25 lb bags. We use the same weight per cubic inch for both.
  • Typical prices (checked Oct 2026): $22–$33 for a 25 lb bag of sanded grout, $18–$20 for a 10 lb bag of unsanded. Epoxy and premixed grouts are sold by the gallon or the pail and cover differently; use their chart.

Worked example

100 sq ft of 12 × 12 in tile, 3/8 in thick, 1/8 in joints

  1. Joint per sq ft: 144 × (12 + 12) ÷ (12 × 12) = 24 in
  2. 100 × 24 × 0.125 × 0.375 × 0.0672 = 7.6 lb
  3. 7.6 ÷ 25 → 1 bag of sanded grout

Sq ft per 25 lb bag: our formula vs the maker's chart

Square feet one 25 lb bag of sanded grout covers, by tile and joint width
Tile1/8 in, ours1/8 in, chart1/4 in, ours1/4 in, chart
4-1/4 × 4-1/4 × 1/4 in17619288101
6 × 24 × 3/8 in265279132143
12 × 12 × 3/8 in331348165177
12 × 24 × 3/8 in441461220234
18 × 18 × 3/8 in496518248262

Chart: Custom Building Products grout coverage card, Polyblend Plus sanded, "for estimating purposes". Small mosaics (1 × 1 in sheets) use noticeably less than the formula says.

Questions people ask

How much grout do I need for 100 sq ft?

For 12 × 12 in tile with 1/8 in joints, about 7.6 lb, so one 25 lb bag. Smaller tile has more joint per sq ft and takes more: 4-1/4 in wall tile at 1/8 in needs about 14.2 lb.

How far does a 25 lb bag of grout go?

Custom's chart gives about 348 sq ft of 12 × 12 in tile at 1/8 in joints and 177 sq ft at 1/4 in. Small tile and wide joints cut that a lot.

Sanded or unsanded grout?

Unsanded for joints under 1/8 in (it packs into narrow gaps), sanded for 1/8 in and wider (the sand keeps wide joints from shrinking and cracking). At exactly 1/8 in either works; we count sanded.

How much grout for a subway tile backsplash?

50 sq ft of 3 × 6 in subway tile, 5/16 in thick, with 1/16 in joints takes about 4.7 lb: 1 10 lb bag of unsanded grout.