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Polyblend Plus Sanded Grout Calculator: How Many 25 lb Bags?
Enter your area, tile size and joint width to see how many 25 lb (11.34 kg) bags of Polyblend Plus Sanded Grout to buy. The calculator uses a joint-volume formula calibrated against the coverage chart in Custom Building Products TDS-360 (published 3/22/2023), set so it never claims more coverage than the chart. For 12 x 12 in tile with 1/8 in joints, Custom's chart gives 348 sq ft per bag; the calculator gives about 346.
Custom Polyblend Plus Sanded Grout coverage
| Tile | 1/8 in | 3/16 in | 1/4 in | 3/8 in | 1/2 in |
|---|---|---|---|---|---|
| 1 x 1 x 1/4 in | 54 | 40 | 33 | 27 | 24 |
| 2 x 2 x 1/4 in | 96 | 68 | 54 | 40 | 33 |
| 3 x 3 x 1/4 in | 138 | 96 | 74 | 54 | 43 |
| 4 1/4 x 4 1/4 x 1/4 in | 192 | 131 | 101 | 71 | 56 |
| 6 x 6 x 1/4 in | 266 | 181 | 139 | 96 | 75 |
| 8 x 8 x 3/8 in | 234 | 158 | 121 | 83 | 64 |
| 12 x 12 x 3/8 in | 348 | 234 | 177 | 121 | 92 |
| 16 x 16 x 3/8 in | 462 | 310 | 234 | 158 | 121 |
| 18 x 18 x 3/8 in | 518 | 348 | 262 | 177 | 135 |
| 20 x 20 x 3/8 in | 574 | 385 | 291 | 196 | 149 |
| 24 x 24 x 3/8 in | 688 | 461 | 348 | 234 | 177 |
| 6 x 24 x 3/8 in | 279 | 189 | 143 | 98 | 75 |
| 12 x 24 x 3/8 in | 461 | 310 | 234 | 158 | 121 |
| 6 x 36 x 3/8 in | 299 | 202 | 153 | 104 | 80 |
| 9 x 36 x 3/8 in | 416 | 279 | 211 | 143 | 109 |
| 12 x 48 x 3/8 in | 552 | 370 | 279 | 189 | 143 |
Source: Custom Building Products Technical Data Sheet TDS-360: Polyblend Plus Sanded Grout, Published 3/22/2023, read 2026-10-17.
How the calculation works
grout per sq ft = 144 × ((L + W) × J + J²) × T ÷ ((L + J) × (W + J))
units = area × (1 + waste ÷ 100) × grout per sq ft ÷ joint volume one unit fills, rounded up
L and W are the tile length and width, T the tile thickness (the joint is assumed to be filled to full tile depth) and J the joint width, all in inches; the result is in cubic inches. The volume one bag fills is worked back from the manufacturer's coverage chart and set at the lowest value any cell of the chart implies, so for every tile size in the chart this calculator gives the same or less coverage than the data sheet, never more. Tiles not in the chart use the same formula.
Worked example
A 400 sq ft floor of 12 x 12 x 3/8 in tile with 1/8 in joints and 10% extra: 440 sq ft to grout. Each tile plus its share of joint is a 12.125 × 12.125 in square, and the joint part of it holds (12 + 12) × 1/8 + 1/8² = 3.016 sq in, 3/8 in deep. That works out to 1.11 cubic inches of grout per sq ft of floor. One 25 lb (11.34 kg) bag fills about 384 cubic inches of joint, so it covers 384 ÷ 1.11 = 346.5 sq ft. 440 ÷ 346.5 = 1.27, so buy 2 bags.
Custom Polyblend Plus Sanded Grout key specs
| Product type | Tile grout |
|---|---|
| Package | 25 lb (11.34 kg) bag |
| Joint width range | 1/8–1/2 in |
| Coverage (data sheet) | per 25 lb bag: 12 x 12 x 3/8" tile 348 sq ft at 1/8", 234 at 3/16", 177 at 1/4", 92 at 1/2"; 2 x 2 x 1/4" mosaic 96 sq ft at 1/8" (full chart below) |
| Joint width | 1/8" to 1/2" (3.1–12.7 mm); for joints up to 1/8" or tile that sanded grout could scratch, Custom points to Polyblend Plus NonSanded |
| Mixing | 2 qt (1.89 L) clean water per 25 lb bag, 1 pt (0.473 L) per 7 lb box; trowel or mixer under 300 rpm about 3 minutes; slake 5 minutes, remix; do not add water later |
| Pot life | 1–2 hours |
| Cleaning window | at 70°F, spread no more than can be cleaned within 30 minutes of the grout firming; haze off after 3 hours |
| Before grouting | setting mortar cured 24–48 hours unless a rapid-setting mortar was used |
| Cure | keep above 50°F (10°C) for at least 72 hours; exterior: mist for 3 days and protect from rain and snow for at least 7 days |
| Temperature | do not install below 50°F (10°C) or above 100°F (38°C) |
| Sealing | optional; penetrating sealer such as Aqua Mix Sealer's Choice Gold if extra protection is wanted |
| Standards | exceeds ANSI A118.6 and A118.7 without additive; 28-day compressive >3,000 psi, flexural >1,000 psi, shrinkage <0.20%, absorption <5% |
| Not for | movement joints, changes of plane, industrial or harsh-chemical areas, high heat or high-pressure cleaning |
| Packaging | 25 lb (11.34 kg) bag in 40 colors, 7 lb (3.17 kg) box in 15 colors, 50 lb (22.68 kg) bag by special order; US item codes PBPG + color + 25 |
What Polyblend Plus is
Polyblend Plus Sanded Grout from Custom Building Products is a powdered portland cement grout with silica sand, inorganic aggregates and polymer, mixed with water on site. It replaced the original Polyblend, and Custom's data sheet lists the changes as brighter and more consistent finished color, better resistance to efflorescence, and a formula that now meets the ANSI A118.7 high-performance grout standard on its own, without a liquid additive. It produces hard, dense joints meant to resist shrinking, cracking, powdering and wear.
TDS-360 rates it for joints from 1/8 to 1/2 inch on floors, walls and ceilings, interior and exterior, residential and commercial. Listed uses include countertops, tub surrounds, showers, high-traffic areas and submerged conditions such as swimming pools, spas, water features and fountains. Suitable tile includes vitreous, semi-vitreous and non-vitreous ceramic, mosaic, quarry and cement-body tile, impervious porcelain and glass, brick and stone veneer, cement-based precast terrazzo and natural stone.
Bag, box or special-order bag
Polyblend Plus Sanded comes as a 25 lb (11.34 kg) bag in 40 colors and a 7 lb (3.17 kg) box in 15 colors; a 50 lb (22.68 kg) bag can be special ordered in any color in the US. This calculator counts 25 lb bags, because that is the size most floors need and the one the main TDS chart is written for. The data sheet prints a second chart for the 7 lb box, and it tracks weight closely: each cell is about 28 percent of the bag figure. If your result is well under one bag, a 7 lb box may be enough, but check that your color is one of the 15 offered in boxes.
How the calculator works
Grout fills only the gaps between tiles, so the amount depends on how much joint there is per square foot of floor. The calculator treats one tile plus half the joint on each side as a rectangle (L + J) by (W + J), where L and W are the tile length and width and J the joint width. The joint part of that rectangle is (L + W) × J + J² square inches. Multiply by the tile thickness T, because the joint is filled to full tile depth, divide by the rectangle's area, and multiply by 144 to get cubic inches of grout per square foot.
Custom does not publish how much joint volume one bag fills, so that number was worked back from each of the 80 cells in the TDS-360 25 lb chart (16 tile sizes by 5 joint widths). Sixty-six of the cells imply between 383 and 395 cubic inches per bag. The calculator uses 383.8, just under the lowest value in the chart, which comes from 20 x 20 inch tile with 1/8 inch joints. That way, for every tile and joint the chart prints, the calculator shows the same or slightly less coverage than Custom does, never more, and the site's build refuses to publish if that stops being true. Where the chart is noticeably more generous than the formula is the 1 x 1 and 2 x 2 inch mosaics with wide joints; there the calculator stays on the safe side by up to about 20 percent.
After that, the calculator adds your waste allowance to the area, divides by the coverage per bag and rounds up to whole bags. Tile sizes not in the chart use the same formula, so you are not limited to the 16 sizes Custom prints.
Entering your tile and joint
Use the actual tile size rather than the nominal one if they differ much; many "12 x 24" porcelain tiles run slightly under, which adds a little joint per square foot. Measure thickness at the tile edge. The joint menu offers 1/8 to 1/2 inch, matching the product's rating. For narrower joints, or for tile the sand could scratch, such as some ceramic, glass, metal, marble or stone, Custom asks you to test a small area first and suggests Polyblend Plus NonSanded Grout for joints up to 1/8 inch.
A 10 percent waste allowance is a sensible default for floors. When you mix more than one bag at a time, Custom asks you to blend the dry powders first so the color stays even, which is easier if you buy all the bags for a room at once from the same lot.
Mixing and installation notes
Mix each 25 lb bag with 2 quarts (1.89 L) of clean water, or each 7 lb box with 1 pint (0.473 L), using a trowel or a mixer under 300 rpm for about 3 minutes until smooth. Let it slake for 5 minutes, then remix. Remix now and then while you work but do not add water; Custom says extra water weakens the grout and can cause color variation, shrinkage, cracks and pinholes. Pot life is 1 to 2 hours. Discard grout once it is too stiff to work.
The setting mortar should cure 24 to 48 hours before grouting unless it is a rapid-setting type. Lightly dampen very porous tile without leaving water in the joints, fill with a rubber float at 45 degrees and strip the excess at 90 degrees. At 70°F do not spread more than you can clean within 30 minutes of the grout firming; haze can come off after 3 hours with cheesecloth or a wrung-out sponge. Install between 50°F and 100°F and keep the area above 50°F for at least 72 hours. Outdoors, mist the grout for 3 days and protect it from rain and snow for at least 7 days. Sealing is optional; a penetrating sealer adds protection. Use caulk or sealant, not grout, at movement joints and changes of plane.
Check before you buy
The numbers on this page come from TDS-360 published 3/22/2023, downloaded from Custom's website. Custom revises data sheets from time to time, so check the current version linked below if your estimate is close to a bag boundary.
FAQ
How much does a 25 lb bag of Polyblend Plus cover?
It depends on tile size and joint width. Custom's TDS-360 chart gives 348 sq ft per 25 lb bag for 12 x 12 x 3/8 inch tile with 1/8 inch joints, 234 sq ft at 3/16 inch and 177 sq ft at 1/4 inch. Mosaics use far more: 2 x 2 inch mosaic at 1/8 inch joints covers 96 sq ft per bag and 1 x 1 inch mosaic only 54 sq ft. Custom says the chart is for estimating and real coverage depends on installation practice and jobsite conditions.
What about the 7 lb box?
TDS-360 has a separate chart for the 7 lb box, and it scales almost exactly with weight: about 28 percent of the 25 lb bag. For 12 x 12 x 3/8 inch tile with 1/8 inch joints the 7 lb box covers 97 sq ft against 348 sq ft for the bag. This calculator works in 25 lb bags; if you only need a fraction of a bag, one 7 lb box covers roughly 0.28 of the bag figure shown. Note that the 7 lb box comes in 15 colors, the bag in 40.
Why is the calculator's coverage a little lower than the chart?
The calculator uses one joint-volume formula for every tile size, with the volume per bag set just under the lowest value any cell of Custom's chart implies, about 384 cubic inches. For every tile and joint in the chart it gives the same or slightly less coverage than the data sheet, never more. Most cells are within about 1 percent; 1 x 1 and 2 x 2 inch mosaics with wide joints are where the chart is noticeably more generous.
Can I use Polyblend Plus for 1/16 inch joints?
No. TDS-360 rates Polyblend Plus Sanded Grout for joints from 1/8 to 1/2 inch, and the coverage chart starts at 1/8 inch. For narrower joints, or for glass, metal, marble or stone tile that the sand could scratch, Custom suggests Polyblend Plus NonSanded Grout for joints up to 1/8 inch. The joint width menu in this calculator only offers 1/8 to 1/2 inch for that reason.
Polyblend Plus or Prism: does the choice change how much I buy?
Not much in count, but it changes the weight. Custom's 25 lb Polyblend Plus chart and its 17 lb Prism box chart are almost cell-for-cell identical, so one Polyblend Plus bag and one Prism box cover about the same area. Polyblend Plus is a conventional portland cement sanded grout with a 1 to 2 hour pot life and may be sealed with a penetrating sealer; Prism is a lighter calcium aluminate grout that needs no sealing and also handles 1/16 inch joints.
Custom Building Products and Custom Polyblend Plus Sanded Grout are trademarks of their owner. This page is an independent estimate based on the published data sheet; check the bag label before mixing.