TileQuantCoverage math for tile, thinset and grout — before you buy.

Grout for 500 ft² of 3×6″ subway tile with 1/2″ joints

Grout needed
358.1lb
15 × 25 lb bags for 500 ft² of 3″ × 6″ subway with 0.5″ joints
25 lb bags15bags
10 lb bags36bags
Dry grout weightincludes 10% waste358.1lb
Grout volume3.26ft³
Joint lengththis, not the floor area, is what drives the quantity3,000linear ft
Joint depththe tile thickness for 3″ × 6″ subway0.3125in
Grout type0.5″ is ⅛″ or widerSanded
Area
500 ft²
Tile size
3×6″ subway
Joint width
1/2 in

Grout follows joint length, not floor area

This is the calculation people get wrong, and they get it wrong in a predictable direction. Grout fills the space between tiles, so what matters is the total length of joint — and that goes up as the tile gets smaller.

500 ft² of 3×6″ subway tile has 3,000 linear ft of joint. At 1/2″ wide and 0.3125″ deep that is 358.1 lb of dry grout, or 15 × 25 lb bags.

Any estimate quoted as "pounds per square foot" without asking the tile size is a guess. The same floor in 2″ mosaic eats several times this.

sanded grout, and it is not a preference

At 1/2″ the answer is sanded. Joints ⅛″ and wider take sanded grout — the sand is structural and stops the grout shrinking and cracking as it cures. Narrower than that, sand physically cannot pack in, and forcing sanded grout into a tight joint leaves voids behind a surface that looks fine.

Unsanded also goes on polished stone and glass regardless of joint width, because sand scratches the face.

Buy one bag more than this

Running out mid-floor is worse than it sounds. The second batch cures at a different rate and often dries a visibly different shade — colour lots vary between bags, and so does how long the mix sat before it went down.

Notes

  • Grout follows joint length, not floor area. 500 ft² of 3″ × 6″ subway has 3,000 linear ft of joint; the same floor in 2″ mosaic would have roughly 6,000 ft and eat several times the grout. Any estimate given as "pounds per square foot" without asking the tile size is guessing.
  • Sanded grout at 0.5″. The sand is structural — it stops the grout shrinking and cracking as it cures across a wide joint.
  • Buy one more bag than the number here. Running out mid-floor means the second batch cures at a different rate and often dries a visibly different shade — colour lots vary, and so does how long the mix sat.
  • Joint depth is assumed equal to the tile thickness (0.3125″). If the thinset squeezed up into the joints, the real depth is less and you will use less grout than this — clean the joints out before the thinset sets rather than grouting over it.

Nearby sizes