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This grout calculator estimates how much grout you need for a tiling job. Enter the area, the tile size and thickness and the joint width, and it uses the standard manufacturer formula to give the grout weight per square foot or square meter and the number of bags to buy.
How to Use the Grout Calculator
- Enter the tiled area.
- Enter the tile length, width and thickness.
- Enter the joint width you will use.
- Enter the bag size and a waste allowance.
Grout Formula
Grout (kg/m²) = (A + B) ÷ (A × B) × C × D × 1.6
A and B are the tile length and width, C is the joint width and D is the joint depth (usually the tile thickness), all in millimeters. The factor 1.6 is the density of cement grout in kg per liter. Manufacturers such as MAPEI publish this formula on their grout data sheets.
Example
100 sq ft of 12 × 12 in tile, ⅜ in thick, with ⅛ in joints uses about 0.065 lb of grout per sq ft. With 10% extra that is about 7.2 lb, so one 10 lb or 25 lb bag is enough.
Grout Needed by Tile Size
Approximate grout per 100 sq ft with ⅛ in joints and ⅜ in thick tile:
| Tile size | Grout per 100 sq ft |
|---|---|
| 2 × 2 in | 39.0 lb |
| 4 × 4 in | 19.5 lb |
| 6 × 6 in | 13.0 lb |
| 3 × 12 in | 16.3 lb |
| 12 × 12 in | 6.5 lb |
| 12 × 24 in | 4.9 lb |
| 24 × 24 in | 3.3 lb |
Small tiles and mosaics use much more grout because they have far more joints per square foot.
Sanded or Unsanded Grout?
- Unsanded grout: joints narrower than ⅛ in, and polished stone or glass that sand could scratch.
- Sanded grout: joints ⅛ in and wider; stronger and less prone to shrinking.
- Epoxy grout: stain-proof and waterproof, good for kitchens and showers, but harder to work.
Count your tiles with the tile calculator.
Sources
Frequently Asked Questions
How much grout do I need for 100 square feet?
For 12 × 12 in tile with ⅛ in joints, about 7 lb. For 4 × 4 in tile it is roughly 20 lb, and mosaics need even more.
How many square feet does a 25 lb bag of grout cover?
It depends on tile and joint size: from about 60 sq ft for 2 in mosaics to over 300 sq ft for 12 × 12 in tile with ⅛ in joints.
How do you calculate grout?
Grout (kg/m²) = (tile length + tile width) ÷ (length × width) × joint width × joint depth × 1.6, with all dimensions in millimeters.
Should grout lines be ⅛ or 1/16 inch?
Rectified tiles can use 1/16 in joints; most floor tiles use ⅛ in or wider to allow for size variation.
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