Match the grout chart to the tile and joint
This tool uses the selected 25-pound Polyblend Plus sanded grout coverage chart. Tile length, width, thickness and joint width all matter. A coverage figure for another tile or grout product is not interchangeable.
One small floor versus four times the area
For 12 × 12 × 3/8-inch tile with a 1/8-inch joint, the selected chart gives 348 square feet per bag. A 10 × 10-foot floor needs 100 ÷ 348 = 0.287 bags, so buy one whole bag before any extra allowance. A 20 × 20-foot floor needs 400 ÷ 348 = 1.149 bags, so buy two.
Doubling both room dimensions multiplies the area by four, but the purchase rises from one bag to two because packages are rounded. The unused portion of a bag is not the same thing as an intentional waste allowance.
When the calculator gives no answer
An unsupported tile size or joint selection means the chart does not provide a supported estimate here. Check the grout manufacturer's current coverage tool or ask for a product-specific takeoff rather than guessing between rows. This particular sanded-grout selection does not cover joints below 1/8 inch.
Check suitability before quantity
Confirm that the grout is suitable for the tile surface, joint width and application. The calculator cannot assess scratching risk, movement joints or a waterproofing system. Keep mortar, grout and sealant as separate products in the budget.
Record the selected color and bag size on your shopping list. Check storage and mixing directions before deciding whether to reuse an opened bag. Use the tile calculator for tile and mortar quantities.