Tile guide

How to read a grout coverage chart

Reviewed October 6, 2026 · By the Room Calculators team · How we check facts

Grout coverage is not one number. Manufacturers publish a chart that lists how many square feet one bag covers for each combination of tile size, tile thickness, and joint width. Reading the right row is the whole job.

What the chart is measuring

Grout fills the gaps between tiles, so the amount depends on how much joint there is per square foot. Smaller tiles mean more joints. Thicker tiles mean deeper joints. Wider joints hold more grout. Change any one of these and the coverage changes, sometimes by a lot.

Reading it, step by step

1. Find the chart for your exact product and bag size.
2. Pick the row for your tile’s length and width.
3. Match the tile thickness if the chart lists it.
4. Read across to the column for your joint width.
5. That cell is the area one bag covers.

For example, CUSTOM Building Products’ data sheet for its 25 lb Polyblend sanded grout lists about 348 sq ft per bag for 12 × 12 in tile with 1/8 in joints. The same bag covers far less with small mosaic tiles or wide joints, which is why the number only applies to that exact row.

Turning it into bags

MAPEI suggests planning a 5–10% overage. A 100 sq ft floor at 348 sq ft per bag with 10% extra uses about a third of a bag, so you buy one.

Common mistakes

• Using a coverage figure from a different brand or bag size.
• Reading the row for a larger tile than you are installing.
• Forgetting that premixed tubs list coverage differently from powder.
• Ignoring the joint width your tile spacers will create.

References: CUSTOM Polyblend Sanded Grout data sheet; MAPEI product calculators