Grout Calculator
Estimate how much grout to buy from your tile size, tile thickness, and joint width. Get pounds of grout and the number of bags, or enter your bag’s own coverage figure.
Grout calculator
Enter the area and your tile, then choose the joint width you plan to use.
Grout coverage chart per 25 lb bag
Approximate square feet covered by one 25 lb bag of cement grout. Values come from the same formula as the calculator above and exclude the extra allowance. Use them to compare options; use your product’s chart to order.
| Tile size | Thickness | 1/16″ joint | 1/8″ joint | 3/16″ joint | 1/4″ joint |
|---|---|---|---|---|---|
| 1" × 1" mosaic | 1/4" | 37 sq ft | 19 sq ft | 12 sq ft | 9 sq ft |
| 2" × 2" mosaic | 1/4" | 74 sq ft | 37 sq ft | 25 sq ft | 19 sq ft |
| 3" × 6" subway | 5/16" | 119 sq ft | 59 sq ft | 40 sq ft | 30 sq ft |
| 4" × 4" | 1/4" | 148 sq ft | 74 sq ft | 49 sq ft | 37 sq ft |
| 6" × 6" | 5/16" | 178 sq ft | 89 sq ft | 59 sq ft | 44 sq ft |
| 4" × 12" | 5/16" | 178 sq ft | 89 sq ft | 59 sq ft | 44 sq ft |
| 12" × 12" | 3/8" | 296 sq ft | 148 sq ft | 99 sq ft | 74 sq ft |
| 12" × 24" | 3/8" | 395 sq ft | 198 sq ft | 132 sq ft | 99 sq ft |
| 24" × 24" | 3/8" | 593 sq ft | 296 sq ft | 198 sq ft | 148 sq ft |
| 24" × 48" | 3/8" | 790 sq ft | 395 sq ft | 263 sq ft | 198 sq ft |
The chart shows what drives grout use. Halving the tile size roughly doubles the grout, because there are twice as many joints in each square foot. Doubling the joint width also doubles it. A 24-inch tile can cover ten times the area per bag that a 2-inch mosaic does.
How the grout calculator works
Every tile shares its edges with its neighbours, so each tile module of length L and width W carries L + W of joint. Dividing by the module’s area gives joint length per square inch. Multiplying by 144, the joint width, and the joint depth (normally the tile thickness) gives the volume of grout in each square foot:
Grout (lb per sq ft) = joint volume × 0.15
The 0.15 lb per cubic inch factor is the important part. If you convert joint volume to weight with the textbook density of dry cement grout, you get about two and a half times more coverage than US manufacturers print on their bags. Real jobs lose grout to fuller joints, mixing, and sponge cleanup. We calibrated the factor to a published manufacturer chart (Custom Building Products Polyblend Plus, 25 lb bag: about 80 sq ft for 4¼-inch tile, ¼ inch thick, with 1/8 inch joints). This keeps the estimate in line with what the bag tells you, so you are less likely to run short halfway through grouting.
Worked example: 60 sq ft shower floor in 2″ × 2″ mosaic
Grout = 4.5 × 0.15 = 0.675 lb per sq ft
60 sq ft × 0.675 = 40.5 lb, + 10% = 44.6 lb → two 25 lb bags
Compare that with 60 sq ft of 12 × 24 inch porcelain at the same joint: about 7.6 lb, so one 10 lb bag. Same area, a sixth of the grout. That is why area alone cannot tell you how much grout to buy.
Before you buy grout
- Sanded or unsanded: sanded grout is generally used for joints 1/8 inch and wider; unsanded for narrower joints and for surfaces sand could scratch. Check the joint range on the bag.
- Epoxy and premixed grout: these come in different package sizes and cover differently. Use the manufacturer’s coverage figure in the optional field.
- Buy one color lot: grout color can shift between production batches. Buy all your bags together and keep the lot number.
- Mosaic sheets: irregular mosaics such as penny rounds have uneven joints, so the rectangular formula is only a rough guide. Rely on the manufacturer’s figure.
Haven’t measured the area yet? Start with the tile calculator, then estimate setting mortar with the thinset calculator. For joint-width choices, see how big grout lines should be, and for a longer explanation read how much grout do I need.
Frequently Asked Questions
- How much grout do I need for 100 square feet?
- It depends on the tile. For 12x12 inch porcelain (3/8 inch thick) with 1/8 inch joints, plan on about 17 lb, so one 25 lb bag with room to spare. The same 100 sq ft of 2x2 inch mosaic with 1/8 inch joints needs about 68 lb, or three 25 lb bags after a 10% allowance.
- How many square feet does a 25 lb bag of grout cover?
- Anywhere from about 19 sq ft (1-inch mosaic) to more than 296 sq ft (24x24 inch tile) at a 1/8 inch joint. Smaller tiles and wider joints use more grout per square foot, so a single coverage number is never right for every job.
- What is the grout calculation formula?
- Joint volume per square foot = 144 × (tile length + tile width) ÷ (tile length × tile width) × joint width × joint depth, with every dimension in inches. Multiply by about 0.15 lb per cubic inch, which we calibrated to a published US manufacturer coverage chart, to get pounds per square foot.
- Should I trust this calculator or the grout bag?
- The bag. Formulations differ, and the manufacturer’s chart reflects its own product. Enter the bag’s coverage in the optional field and the calculator will use it to work out the number of bags.
- Does joint depth matter?
- Yes. Grout fills the joint down to the setting bed, so thicker tile holds more grout. A 3/4 inch paver uses twice the grout of a 3/8 inch porcelain tile of the same size and joint width.
Tiling a different surface?
Choose a surface-specific quantity estimate, or build a bathroom installation budget with your own material and labor rates. For other projects, use the main tile estimator.
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Estimate wall tiles wall-by-wall and subtract windows and doors as you go.
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Plan floors, walls, and wet areas, with a separate estimate for each tile product.
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Measure a shower surround, pan, and niche, then get tiles plus a realistic waste buffer.
Backsplash tile calculator
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Thinset calculator
Bags of thinset mortar for your area, based on the trowel notch you use.