Grout Calculator
Work out the pounds and bags of grout for a tile floor, wall or backsplash.
How to use the Grout Calculator
- Enter the area to grout and pick its unit.
- Enter the tile length and pick its unit.
- Enter the tile width and pick its unit.
- Enter the tile thickness and pick its unit.
- Enter the grout joint width and pick its unit.
- Choose the bag size.
- Enter the waste allowance.
- Press Calculate. The result updates automatically as you type, and you can switch the result unit at any time.
About the Grout Calculator
Grout use depends far more on tile size and joint width than on area. Small mosaics have many joints and can use five to ten times as much grout per square foot as large-format tile. Use unsanded grout for joints under ⅛ in, and sanded grout for ⅛ in and wider, unless you choose a premixed or epoxy product rated for both.
Mix only what you can apply in about 30 minutes, and keep a little extra from the same color batch for future repairs. Seal cement grout once cured, usually after 48–72 hours.
Formula
Joint volume = Area × (Tile length + Tile width) ÷ (Tile length × Tile width) × Joint width × Tile thickness
Grout weight ≈ Joint volume × 1.85 kg/L (≈ 115 lb/ft³) × (1 + waste %)
The first term is the length of joint per unit of tiled area: each tile contributes one length and one width of joint. The density is a typical value for cured cement grout; manufacturers' coverage charts can differ by 10–20%.
Example calculation
Using the default values:
- Area to grout = 100 ft²
- Tile length = 12 in
- Tile width = 12 in
- Tile thickness = 3/8 in
- Grout joint width = 1/8 in
- Bag size = 25 lb
- Waste allowance = 10%
the calculator returns:
- Grout needed: 8.3 lb
- Bags: 1 bags
- Joint volume: 112.5 in³
- Coverage per bag: 302 sq ft
Frequently asked questions
How much grout do I need for 100 sq ft?
With 12 × 12 in tile, ⅜ in thick and ⅛ in joints, about 8 lb including waste, so one 10 lb bag. With 1/4 in joints on 4 × 4 in tile it is closer to 50 lb.
Should I use sanded or unsanded grout?
Use unsanded grout for joints narrower than ⅛ in and for easily scratched surfaces like polished marble; use sanded grout for wider joints.
How long does grout take to cure?
Cement grout is usually ready for light foot traffic in 24 hours and for sealing after 48–72 hours. Check the bag for the product’s timing.
Last updated: · Category: Construction calculators