Grout Calculator — How Much Grout Do You Need?
Grout use depends on tile size and joint width — small tiles with wide joints need far more. Enter your tile and joint details to estimate the grout in pounds and 25 lb bags.
How to use this calculator
- Enter the area you are grouting and your tile dimensions in inches.
- Set the joint width — wider joints (and smaller tiles) use much more grout.
- Set joint depth to the tile thickness; thicker tiles mean deeper, fuller joints.
- This is an estimate — buy a little extra and mix from the same lot for color consistency.
The formula
Grout fills the joints between tiles, so the amount depends on joint volume.
Grout per sq ft ≈ joint width × joint depth × (tile length + tile width) ÷ (tile length × tile width). Smaller tiles have more joint per area, so they use more grout.
Weight = joint volume × grout density (≈0.058 lb per cubic inch), divided into 25 lb bags and rounded up.
Worked example
100 sq ft of 12 × 12 in tile, 1/8 in joints, 3/8 in thick.
Per sq ft ≈ 0.125 × 0.375 × (24 ÷ 144) × 144 = 1.13 cu inTotal = 1.13 × 100 = 112.5 cu inWeight = 112.5 × 0.058 ≈ 6.5 lb → 1 bag
About 6.5 lb of grout — one 25 lb bag easily covers 100 sq ft of 12×12 tile with 1/8 in joints.
Frequently asked questions
How much grout do I need?
It depends on tile size and joint width. Large tiles with thin joints use very little; small mosaics with wide joints use a lot. Enter your specifics above for an estimate in pounds and bags.
Sanded or unsanded grout?
Use sanded grout for joints 1/8 inch and wider, and unsanded grout for joints narrower than 1/8 inch (it would scratch polished stone and glass otherwise).
Why buy extra grout?
Mix all your grout from the same lot to avoid slight color shifts between batches, and keep a little spare for repairs. Estimates assume full, well-packed joints.