Grout for 400 ft² of 3×6″ subway tile with 3/8″ joints
| 25 lb bags | 9bags |
|---|---|
| 10 lb bags | 22bags |
| Dry grout weightincludes 10% waste | 214.8lb |
| Grout volume | 1.95ft³ |
| Joint lengththis, not the floor area, is what drives the quantity | 2,400linear ft |
| Joint depththe tile thickness for 3″ × 6″ subway | 0.3125in |
| Grout type0.375″ is ⅛″ or wider | Sanded |
- Area
- 400 ft²
- Tile size
- 3×6″ subway
- Joint width
- 3/8 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.
400 ft² of 3×6″ subway tile has 2,400 linear ft of joint. At 3/8″ wide and 0.3125″ deep that is 214.8 lb of dry grout, or 9 × 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 3/8″ 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. 400 ft² of 3″ × 6″ subway has 2,400 linear ft of joint; the same floor in 2″ mosaic would have roughly 4,800 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 0.375″. 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
- Grout for 360 ft² of 3×6″ subway tile with 3/8″ joints
- Grout for 450 ft² of 3×6″ subway tile with 3/8″ joints
- Grout for 320 ft² of 3×6″ subway tile with 3/8″ joints
- Grout for 500 ft² of 3×6″ subway tile with 3/8″ joints
- Grout for 400 ft² of 2×2″ mosaic tile with 3/8″ joints
- Grout for 400 ft² of 4×4″ tile with 3/8″ joints
- Grout for 400 ft² of 6×6″ tile with 3/8″ joints
- Grout for 400 ft² of 3×6″ subway tile with 1/4″ joints
- Grout for 400 ft² of 3×6″ subway tile with 1/2″ joints
- Grout for 400 ft² of 3×6″ subway tile with 3/16″ joints
Read more
- What a 25 lb Bag of Grout Actually CoversA bag's coverage figure is real. It is also stated for one specific tile size, joint width and thickness — change any of the three and the number moves by a lot.
- Grout for Subway Tile: Three Times the 12-Inch FigureSubway tile is the highest grout consumption per square foot of any common format. If you sized the order from a floor tile figure, you are about a third of the way there.
- Grout for 12 × 24 Tile: Why the Big Format Uses LessLarge format tile is the one place where the bigger product costs you less of something. Grout is that something, and the saving is exactly a quarter.
- Sanded or Unsanded: The Joint Width That Decides ItThe dividing line is 1/8 inch and it is not a style guideline. Using the wrong one on either side of it produces a specific, predictable failure.