How Much Thin-Set and Grout Do I Need?

Thin-set depends on the trowel: a 50 lb bag covers about 60–67 sq ft with a 1/4 × 3/8 in notch. Grout depends on the joints: 100 sq ft of 12 × 24 in tile with 1/8 in joints takes about 5.4 lb.

Updated October 7, 2026

Thin-Set: It’s the Trowel

The notch on your trowel sets how thick the mortar bed is. CUSTOM Building Products lists this coverage for VersaBond thin-set:

Trowel (square notch)	Coverage per 50 lb bag
1/4 × 1/4 in	90–100 sq ft
1/4 × 3/8 in	60–67 sq ft
1/2 × 1/2 in	42–47 sq ft

Bags = area ÷ coverage per bag, rounded up

CUSTOM calls for at least 80% mortar contact in dry areas and 95% in wet areas and outdoors. Large tiles often need a bigger notch and back-buttering to get there, so they use more mortar than the table suggests.

Grout: It’s the Joints

Grout fills the gaps between tiles. The volume per square foot depends on how much joint each tile has, and how wide and deep it is:

Grout per sq ft ∝ (tile length + width) ÷ (tile length × width) × joint width × tile thickness

Using a density matched to CUSTOM’s Polyblend Plus sanded grout chart, here’s grout per 100 sq ft:

Tile	1/16 in joints	1/8 in joints	1/4 in joints
6 × 6 × 1/4 in	4.8 lb	9.6 lb	19.2 lb
6 × 24 × 3/8 in	4.5 lb	9.0 lb	18.0 lb
12 × 12 × 3/8 in	3.6 lb	7.2 lb	14.4 lb
12 × 24 × 3/8 in	2.7 lb	5.4 lb	10.8 lb
24 × 24 × 3/8 in	1.8 lb	3.6 lb	7.2 lb

Smaller tiles mean more joints per square foot, so mosaics and subway tile use far more grout than large-format tile.

Buy a Little Extra

Joints vary in width, some grout is lost in cleanup, and you’ll want a little for repairs. CUSTOM points out that a 1/32 in difference in joint width changes the grout needed by 25%. The tile calculator works out tiles, thin-set, and grout together for your tile and room.

Frequently Asked Questions

Which Trowel Size Should I Use?

Bigger tiles need bigger notches to get full mortar contact. Follow the tile and mortar makers’ recommendations, and lift a tile now and then to check coverage.

Why Does Grout Coverage Vary So Much?

Grout fills the joints, so wider joints and thicker tiles use much more. CUSTOM notes that joints just 1/32 in wider than planned use 25% more grout.

Sanded or Unsanded Grout?

Sanded grout is for wider joints; unsanded for narrow ones. Check the grout’s label for the joint widths it’s rated for.

Sources

Prices are national ballparks checked October 2026. Local prices vary.