Grout is sold by weight, often in bags of 25 lb, but it fills a volume: a strip in every joint, as deep as the tile is thick. The calculator converts that volume to pounds at 110 lb per cubic foot. That figure was worked back from a grout maker's coverage chart for sanded cement grout, so treat the pounds as an estimate.
How to use this calculator
- Measure the floor's length and width in feet. For a wall, use its width as the length and the height you will tile as the width. Need the room area first? The flooring calculator reports it.
- Enter the tile size from the box, length first. Tile size takes inches or centimeters, and joint width and thickness take inches or millimeters.
- Enter the joint width you will set with your spacers. Boxes usually list only the tile size, so the joint is your choice, and a wider joint takes more grout.
- Measure one tile's thickness and enter it as the joint depth. The calculator assumes every joint is filled to that depth, so shallower joints use less grout than the result.
- Compare the coverage of one bag with the chart on the bag you will buy. If they disagree, trust the chart, and buy every bag in one order to keep one batch.
Worked examples
Mosaic shower floor
Size: 4 × 5 ft · Tile: 2 × 2 in · Joint width: 0.125 in · Tile thickness: 0.25 in
- Grout
- 5.4 lb
- 25 lb bags
- 1
- Tiled area
- 20 sq ft
- Coverage of one bag
- 93 sq ft
Kitchen floor
Size: 12 × 14 ft · Tile: 12 × 12 in
- Grout
- 11.9 lb
- 25 lb bags
- 1
- Tiled area
- 168 sq ft
- Coverage of one bag
- 353 sq ft
Living room in large tiles
Size: 20 × 20 ft · Tile: 24 × 24 in · Joint width: 0.25 in
- Grout
- 28.4 lb
- 25 lb bags
- 2
- Tiled area
- 400 sq ft
- Coverage of one bag
- 353 sq ft
Subway tile wall
Size: 8 × 6 ft · Tile: 3 × 6 in
- Grout
- 10.0 lb
- 25 lb bags
- 1
- Tiled area
- 48 sq ft
- Coverage of one bag
- 120 sq ft
Coverage of one bag for common tile sizes and joint widths
| Tile size | Joint width: 0.125 in | Joint width: 0.25 in | Joint width: 0.5 in |
|---|---|---|---|
| 3 × 6 in | 120 | 62 | 33 |
| 12 × 12 in | 353 | 178 | 91 |
| 12 × 24 in | 469 | 237 | 120 |
| 24 × 24 in | 702 | 353 | 178 |
Each cell: Coverage of one bag (sq ft). Inputs not in the table use the calculator's starting values.
What drives the amount
Grout fills the gaps between tiles, so the amount depends on how many gaps there are, how wide they are and how deep they go. Small tiles leave joints across the whole surface, so a mosaic floor takes far more grout per square foot than a floor of large tiles with the same joint width.
Width and thickness multiply into the result, so a wider joint or a thicker tile always means more grout. Walls follow the same rules: enter the wall's width as the length and its height as the width.
The table shows how far one bag goes. Read down a column and coverage rises as the tiles get larger; read across a row and it falls as the joints widen. For the number of pieces to buy, use the tile calculator.
How the calculation works
Across one square foot, joints run in both directions. The calculator adds up their length, multiplies it by the joint width and the tile thickness to get the grout volume in that square foot, then scales it to your area.
Volume becomes weight at 110 lb per cubic foot, and the bag count rounds up to whole bags. The coverage of one bag is the best check: if the chart on your bag gives a very different area for the same tile and joint, it is probably a different grout, and the pounds will not match.
Mistakes to avoid
- Using the tile box for the joint. Boxes give the tile size, not the gap.
- Measuring the whole room. Grout only goes where tile goes, so leave out cabinet bases, tubs and other untiled areas.
- Assuming every joint is full. Shallower joints use less grout than the result.
- Buying bags over several trips. Color can vary between production batches, so buy them together.
Common questions
How much grout do I need per square foot?
There is no single figure, since it depends on the tile size, joint width and thickness. The calculator gives the pounds for your exact settings, and a small tile with wide joints needs far more per square foot than a large tile with narrow joints.
How far does one bag of grout cover?
It depends on the tile and the joint, so the calculator shows the coverage of one bag for your settings. The calculator counts bags of 25 lb, so check the coverage against the chart printed on your bag.
Can I use this calculator for epoxy or unsanded grout?
Only as a rough guide. The weight here is for sanded cement grout, and epoxy and unsanded products weigh differently, so use the coverage chart on the bag instead.
Does the grout calculator add extra for waste?
No. It works out what the joints take and rounds up to whole bags, so the last bag usually has some left over for repairs.
Is this a concrete grout calculator?
No. This calculator is for the joints between tiles. Grout that fills concrete block cores or sits under a base plate is a different product, and it is measured by the volume of the space it fills.
Should I use sanded or unsanded grout?
Grout makers generally switch at a joint width of 0.125 inch: use unsanded grout for narrower joints and sanded grout for joints that wide or wider. Check the bag for the joint widths it is made for. This calculator uses the weight of sanded grout.