How many bags of grout for 100 square feet?

The number of grout bags needed for 100 sq ft depends on tile size and joint width. For 12×12 inch tiles with a 3/16 inch joint, one 10-lb bag covers about 50 sq ft, so you need roughly 2 bags. For smaller 4×4 inch tiles with a ¼ inch joint, one 10-lb bag covers only about 15 sq ft, requiring about 7 bags. Always add 10% extra for waste and future repairs.

How much thinset do I need per square foot?

A standard 50-lb bag of thinset mortar covers approximately 40–50 sq ft when applied with a 3/16 inch V-notch trowel, or 35–40 sq ft with a ¼×¼ inch square-notch trowel. For large-format tiles (18×18 inches or larger), use a ½×½ inch notch trowel, which consumes more mortar at about 25–35 sq ft per 50-lb bag. Back-buttering large tiles adds additional mortar consumption.

What joint width should I use for 12x12 tiles?

For 12×12 inch ceramic or porcelain floor tiles, a 3/16 inch (4.8 mm) grout joint is the industry standard. This width accommodates normal size variation in the tiles (called rectification tolerance) while creating a clean, proportional look. For rectified (precision-cut) tiles, you can go as narrow as 1/16 inch. For natural stone 12×12 tiles, a ¼ inch joint is common because stone varies more in size.

Grout and Mortar Coverage Guide: Bags Per Sq Ft and Sq M

Grout Coverage Formula

The theoretical coverage for any grout depends on tile dimensions and joint geometry. The standard industry formula is:

Sq ft per bag = [Tile L × Tile W ÷ ((Tile L + Joint) × (Tile W + Joint))] × Bag Coverage Factor

In practice, use the coverage tables below as a starting point, then add 10% for waste. Actual coverage varies by joint depth, tile surface texture (porous vs. glazed), and mixing consistency.

Grout Coverage: Sq Ft per 10-lb Bag by Tile Size and Joint Width

Tile Size	1/16 in Joint	1/8 in Joint	3/16 in Joint	1/4 in Joint	1/2 in Joint
2 × 2 in (mosaic)	5	4	3	2.5	—
4 × 4 in	25	18	14	11	—
6 × 6 in	40	28	22	17	—
12 × 12 in	90	65	50	38	22
18 × 18 in	130	95	72	55	30
24 × 24 in	170	125	95	73	40

Thinset Mortar Coverage: Sq Ft per 50-lb Bag by Trowel Notch

Trowel Notch Size	Coverage per 50-lb Bag (sq ft)	Recommended For
3/16 in V-notch	40 – 50	Wall tile, small floor tiles up to 4×4 in
¼ × ¼ in square-notch	35 – 45	Floor tiles 6×6 to 12×12 in
¼ × &frac38; in square-notch	30 – 40	Floor tiles 12×12 to 16×16 in
&frac38; × &frac38; in square-notch	25 – 35	Larger tiles 16×16 to 18×18 in
½ × ½ in square-notch	20 – 30	Large-format tiles 18×18 in and up

Tips for Accurate Estimates

Always purchase 10% more grout and thinset than calculated to allow for waste and corrections.
Keep one extra bag of each from the same lot number for future repairs — color matching is difficult across lots.
Back-buttering (applying mortar to the back of the tile) increases thinset use by 15–20%.
Large-format tiles (>15 in) require at least 95% mortar coverage, which means using a larger notch trowel and back-buttering every tile.

Use our area converter to switch between sq ft and sq m when working from European tile specifications or metric construction plans.