Paint & Flooring
Grout Calculator
Estimate how much tile grout you need for a floor, wall or backsplash. Enter the tiled area, tile size and thickness, and joint width, and this grout calculator works out the joint volume, the pounds of grout and the bags to buy, with an optional cost.
Result
Enter your measurements and press Calculate. What to buy, the working and the cost will appear here.
How to use the grout calculator
- Enter the tiled area. The tile calculator or square footage calculator can work it out.
- Enter the tile size and thickness; grout fills the joint to the full tile thickness.
- Enter the joint width and choose the bag size.
- Press Calculate for pounds, bags and cost.
How grout is calculated
Grout fills the joints, so the amount depends on how many joints there are per square foot, how wide and how deep they are:
joint length per area = (tile length + tile width) ÷ (tile length × tile width)
grout volume = area × joint length per area × joint width × tile thickness
Small tiles have far more joints per square foot than large ones, which is why mosaics use much more grout than 24 in tiles for the same floor.
Worked example: 100 ft² of 12 × 12 tile
100 ft² of 12 × 12 in tile, 3/8 in thick, with 1/4 in joints and 25 lb bags at $22:
- Joint length per area: (12 in + 12 in) ÷ (12 in × 12 in)
- Joint volume: 100 ft² × joint length × 0.25 in wide × 0.375 in deep = 225 in³
- Weight: 225 in³ × 1.1 × 1.6 kg/L = 14.3 lb
- Bags: 14.3 lb ÷ 25 lb bag → 1 bag
Bags of grout: 1 bag; Grout needed: 14.3 lb; Coverage: 7 ft² per lb; Estimated cost: $22.00. Open this example in the calculator.
Sanded or unsanded grout?
- Unsanded grout for joints up to 1/8 in, polished stone and wall tile that scratches easily.
- Sanded grout for joints of 1/8 in and wider; the sand stops it shrinking and cracking.
- Epoxy grout for showers, kitchens and high-stain areas; it follows its own coverage chart.
Grout rules of thumb
- 12 × 12 in tile with 1/8 in joints, 3/8 in thick: about 6.5 lb per 100 ft².
- The same tile with 1/4 in joints: about 13 lb per 100 ft².
- 2 × 2 in mosaic with 1/8 in joints, 1/4 in thick: about 25–30 lb per 100 ft².
Mix only what you can use in about 30 minutes, and buy an extra bag of the same color lot for touch-ups.
Assumptions and limitations
- Joints are filled to the full tile thickness and are the same width throughout.
- Cured grout weighs about 1.6 kg per liter; manufacturers’ charts may differ slightly by product.
- Thinset mortar under the tile is not included.
Grout questions
How much grout do I need for 100 square feet?
For 12 × 12 in tile, 3/8 in thick: about 6.5 lb with 1/8 in joints, about 13 lb with 1/4 in joints, before waste. Smaller tiles need much more.
How many square feet does a 25 lb bag of grout cover?
For 12 × 12 tile with 1/8 in joints, roughly 380 ft²; with 1/4 in joints, about 190 ft². For small tiles it can be under 100 ft².
Formulas, unit conversions and default values are explained on our methodology page. Results are estimates; check manufacturer data and local codes before you buy or build.