Grout Calculator

Grout formula

Grout per sq ft (in³) = (L + W) ÷ (L × W) × joint width × tile thickness × 144

L and W are the tile length and width in inches. Smaller tiles and wider joints need much more grout.

Worked example

12 × 12 in tiles, 3/8 in thick, with 1/8 in joints need (24 ÷ 144) × 0.125 × 0.375 × 144 = 1.125 in³ per sq ft. For 100 sq ft plus 10% waste that is about 124 in³, or roughly 8 lb of cement grout.

Tips

• Use sanded grout for joints 1/8 in and wider, unsanded for narrower joints.
• Buy a little extra from the same batch for repairs.
• Mix only what you can use in about 30 minutes.

Frequently asked questions

How much grout for 100 sq ft?

With 12 × 12 tiles and 1/8 in joints, about 7–8 lb. Small mosaics can need several times more.

Does tile thickness matter?

Yes. Grout fills the full depth of the joint, so thicker tile uses more.

What joint width should I use?

Rectified tiles often use 1/16 to 1/8 in; handmade or uneven tiles need wider joints.

Is epoxy grout calculated the same way?

The volume is the same, but epoxy has a different density, so check the product’s coverage chart.