Home › Thinset mortar › Custom ProLite Premium
Custom ProLite Coverage Calculator: How Many 30 lb Bags?
Enter your area and trowel to see how many 30 lb (13.6 kg) bags of ProLite Premium Large Format Tile Mortar to buy. ProLite is a lightweight mortar: CUSTOM says one 30 lb bag covers the same area as a 50 lb bag of traditional mortar. The coverage figures come from its data sheet, TDS-114.
Custom ProLite Premium coverage
| Trowel notch | US | Metric |
|---|---|---|
| 1/4" x 1/4" x 1/4" square notch (6 x 6 x 6 mm square notch) | 90–100 sq ft | 8.4–9.3 m² |
| 1/4" x 3/8" x 1/4" square notch (6 x 9.5 x 6 mm square notch) | 63–70 sq ft | 5.9–6.5 m² |
| 1/2" x 1/2" x 1/2" square notch (not recommended by CUSTOM) (13 x 13 x 13 mm square notch) | 45–50 sq ft | 4.2–4.6 m² |
| 3/4" x 9/16" x 3/8" U-notch held at 30° (19 x 14 x 9.5 mm U-notch at 30°) | 45–50 sq ft | 4.2–4.6 m² |
| 3/4" x 9/16" x 3/8" U-notch held at 45° (19 x 14 x 9.5 mm U-notch at 45°) | 36–40 sq ft | 3.3–3.7 m² |
Source: CUSTOM Building Products Technical Data Sheet TDS-114: ProLite Premium Large Format Tile Mortar, TDS-114, file TDS-114-Prolite-011626.pdf (dated January 16, 2026; the sheet itself prints "Published Date: January 16, 2025"), read 2026-10-17.
How the calculation works
bags = area × (1 + waste ÷ 100) ÷ coverage per bag, rounded up
The manufacturer gives a coverage range for each trowel size because the real figure depends on the tile back, the substrate and how much mortar ends up in the ridges. This calculator divides by the low end of the range, so the number it tells you to buy should not leave you short. If you back-butter large tiles, plan for coverage at or below the low end.
Worked example
A 240 sq ft floor with a 3/4" x 9/16" x 3/8" U-notch held at 30° trowel and 10% extra: 240 × 1.1 = 264 sq ft. At the low end of the coverage range (45 sq ft per bag) that is 264 ÷ 45 = 5.87 bags, so buy 6. That is 180 lb of powder.
Custom ProLite Premium key specs
| Product type | Thinset mortar |
|---|---|
| Bag size | 30 lb (13.6 kg) |
| Mixing water per bag (max) | 6 US qt (5.7 L) |
| Mixing water | 5.75–6 US qt (5.4–5.7 L) per 30 lb bag |
| Mixing | by hand or a 1/2" drill at 150–200 RPM; slake 5–10 minutes, restir; do not add more water |
| Pot life | 4 hours |
| Open time (ANSI A118.15 section 5.3) | 30 minutes (pass) |
| Mortar thickness under tile | 3/32" to 3/4" (2.38–19 mm) continuous, after embedding |
| Time before grouting | 24 hours (also light foot traffic) |
| Heavy or vehicular traffic | after 7–10 days |
| Pools and water features | wait 14 days after the final grouting before filling (water at 70°F / 21°C) |
| Standards | exceeds ANSI A118.4TE, A118.15HET and A118.11; meets ISO 13007 C2TES1P1 |
| Bag sizes and item codes | 30 lb gray (PLMG30) or white (PLMW30) in the US; CPLMG30 / CPLMW30 in Canada |
| Required mortar contact | at least 80% in dry areas, at least 95% in wet areas and exteriors |
What ProLite is, and why the bag is only 30 lb
ProLite Premium Large Format Tile Mortar is CUSTOM Building Products' lightweight thin-set and medium bed mortar for large and heavy tile, on floors and walls, inside and out. The bag weighs 30 lb (13.6 kg) instead of the usual 50 lb, because the mix uses lighter aggregate and is not formulated with silica sand. CUSTOM's data sheet, TDS-114, says the mortar is about 40% lighter than traditional mortar and that one 30 lb bag covers the same area as a 50 lb bag. So when you plan a job, count bags, not pounds: a 30 lb bag of ProLite does the work of a 50 lb bag of a standard mortar.
The data sheet used on this page is the one CUSTOM links from its ProLite product page today. Its file name carries the date January 16, 2026, while the printed header still reads "Published Date: January 16, 2025". The coverage chart and mixing figures below are taken from that file.
ProLite exceeds ANSI A118.4TE, A118.15HET and A118.11 and meets ISO 13007 C2TES1P1, all without a liquid additive, so you mix it with plain water. It is non-sag and non-slump, so it holds wall tile in place and can be used as a medium bed mortar up to 3/4 inch thick. It is also recommended for interior and exterior pools and water features that require an A118.15 mortar.
Trowel choice and the coverage chart
TDS-114 lists five trowel rows, all per 30 lb bag:
- 1/4 x 1/4 x 1/4 inch square notch: 90 to 100 sq ft
- 1/4 x 3/8 x 1/4 inch square notch: 63 to 70 sq ft
- 1/2 x 1/2 x 1/2 inch square notch: 45 to 50 sq ft, with a note that CUSTOM does not recommend this trowel
- 3/4 x 9/16 x 3/8 inch U-notch held at 30 degrees: 45 to 50 sq ft
- The same U-notch held at 45 degrees: 36 to 40 sq ft
The two small square notches suit ordinary floor and wall tile. Large format tile needs a thicker bed, and here CUSTOM steers you away from the 1/2 inch square notch. Its reason is practical: the 1/2 inch spacing between notches makes tile harder to bed and full contact harder to reach. It recommends a trowel whose ridges collapse easily, such as the 3/4 inch U-notch held at about 30 degrees, which uses the same amount of mortar as a 1/2 inch square notch but beds better. That is why the calculator starts on the U-notch at 30 degrees. If you hold the trowel more upright, at 45 degrees, it leaves more mortar on the floor and coverage drops to 36 to 40 sq ft per bag.
Like every calculator on this site, this one uses the low end of each range and rounds up to whole bags. For 100 sq ft plus 10% waste with the default trowel, that is 110 ÷ 45 = 2.4, so 3 bags. With a 1/4 x 3/8 inch square notch the same floor needs 110 ÷ 63 = 1.7, so 2 bags.
Coverage depends on contact
The chart is for estimating only. CUSTOM requires at least 80% mortar contact under the tile in dry areas and at least 95% in wet areas and exteriors, with every tile edge supported, and the bed must end up between 3/32 inch and 3/4 inch thick after the tile is beaten in. Large tile, tile with deep back patterns and ungauged stone may need a bigger notch and flat or notched back troweling, and the mortar you spread on the back of each tile is not in the chart. Add an allowance for it, or raise the waste setting. Pull up a tile now and then to check the back; CUSTOM recommends testing coverage to meet warranty requirements.
What it bonds to
TDS-114 lists concrete, mortar beds, masonry and Portland cement plaster; liquid waterproofing membranes such as RedGard and RedGard SpeedCoat; crack isolation sheets such as Crack Buster Pro; uncoupling mats; and surfaces primed with CUSTOM's MBP primer. Exterior-grade plywood is allowed in interior residential and light commercial dry areas, gypsum wallboard in interior dry areas, and existing ceramic tile, fully bonded sheet vinyl and plastic laminate once scarified. Cutback adhesive must be wet-scraped down to a transparent stain; never sand or grind it, as it may contain asbestos.
Do not bond ProLite directly to hardwood, luan, particle board, parquet, cushion-backed vinyl, metal, fiberglass, plastic or OSB. For moisture-sensitive or resin-backed stone CUSTOM points to its epoxy products, and for clear or translucent glass tile to its Glass Tile mortar.
Mixing and curing
Mix 5.75 to 6 US quarts (5.4 to 5.7 L) of clean water per 30 lb bag, by hand or with a 1/2 inch drill at 150 to 200 RPM, until it is smooth and paste-like. Let it slake 5 to 10 minutes, stir again and use. Pot life is 4 hours and open time is 30 minutes under the A118.15 test. Stir now and then, but do not add water; properly mixed, the ridges stand without slumping. Allow 24 hours before grouting and light traffic and 7 to 10 days before heavy or vehicular traffic. For pools and fountains, wait 14 days after the final grouting before filling with water at about 70°F (21°C).
Common mistakes
- Buying by weight. Someone used to 50 lb bags may buy too many; the chart is per 30 lb bag.
- Using a 1/2 inch square notch on large tile and then fighting hollow spots. Try the U-notch at 30 degrees instead.
- Using thin-set to fill low spots. Flatten the floor first; the bed must stay at or under 3/4 inch.
- Bridging movement joints. They must be carried through the tile and filled with a flexible sealant.
Comparing mortars? The thinset coverage table lists ProLite next to CUSTOM's 50 lb VersaBond-LHT, which has the same trowel rows.
FAQ
How much does a 30 lb bag of ProLite cover?
CUSTOM's TDS-114 chart gives 90 to 100 sq ft with a 1/4 x 1/4 inch square notch, 63 to 70 sq ft with 1/4 x 3/8 inch, 45 to 50 sq ft with a 3/4 inch U-notch held at 30 degrees (the same as a 1/2 inch square notch), and 36 to 40 sq ft with that U-notch held at 45 degrees. The calculator uses the low end of each range.
Does a 30 lb bag of ProLite really cover as much as a 50 lb bag?
That is CUSTOM's claim on the data sheet: the mortar is about 40% lighter than traditional mortar, so a 30 lb bag covers the same area as a 50 lb bag. Its chart bears that out. The figures are the same as or slightly higher than the 50 lb VersaBond-LHT chart for every trowel, so compare bags, not pounds.
Can I use ProLite in a pool or fountain?
Yes. TDS-114 recommends it for interior and exterior pools and water features that call for an ANSI A118.15 mortar. Wait 14 days after the final grouting before filling with water at about 70°F (21°C), and longer if it is colder.
How much water goes into a bag?
5.75 to 6 US quarts (5.4 to 5.7 L) of clean water per 30 lb bag. That is nearly as much water as a 50 lb bag of standard mortar takes, because the bag makes about the same volume of mortar. Mix at 150 to 200 RPM, let it slake 5 to 10 minutes, restir, and do not add more water later.
How thick can I set tile with ProLite?
It is a non-sag, non-slump medium bed mortar, so after the tile is beaten in the bed can be anywhere from 3/32 inch to 3/4 inch (2.38 to 19 mm) thick. It is not meant to fill low spots in the floor; level those first with a patch or self-leveler.
CUSTOM Building Products and Custom ProLite Premium are trademarks of their owner. This page is an independent estimate based on the published data sheet; check the bag label before mixing.