Quikrete CMU Grout Calculator — Core Fill for Concrete Block Walls

That is always a fractional number — grout sells by the bag, blocks sell by the pallet, and the fraction depends entirely on the block size and whether you are filling every course or every fourth course. An 8 × 8 × 16 in CMU block with two core holes holds roughly 180 cubic inches of grout total, which is 0.104 ft³. A 60 lb bag of Quikrete Core Fill Grout yields about 0.53 ft³ of mixed grout. That means one 60 lb bag fills about 5 blocks. For a 20 ft wall at 8 ft tall in 8 × 8 blocks every course: 30 blocks per course × 48 courses = 1,440 blocks → about 288 bags of core fill grout. Do not guess — run the calculator above with your exact wall.

Core fill grout is structural, tile grout is decorative. Quikrete Core Fill has coarse aggregate (1/4 in pea gravel) for compressive strength — every core you fill becomes part of the wall's load-bearing capacity. Tile grout is fine sand for filling 1/8 to 1/4 in joints between tiles — it has zero coarse aggregate. Core fill grout is 4000 psi compressive strength or higher; tile grout is typically 1500–2500 psi. Core fill costs about $20–30 per bag at 60 lb; tile grout costs about $15–30 per bag at 25 lb. They are in completely different product categories — mixing them up in the wrong application creates failures.

Filling every fourth course instead of every course is the standard code minimum for non-reinforced CMU walls. The filled courses become bond beams that distribute lateral loads (wind, seismic) across the wall. A 20 ft wall of 8 × 8 blocks needs 12 bond beam courses instead of 48 filled courses — 1/4 the grout, same structural performance. You fill every course only if you have rebar running vertically through every core (fully grouted reinforced CMU), which requires an engineer's plan. Always check your local code — some jurisdictions require every course filled regardless of rebar.

Standard residential CMU wall: #4 rebar (1/2 in diameter) placed in every other core (16 in on center horizontally), vertically in every course of a bond beam. If you fill every course (reinforced CMU), #4 rebar in every core 24 in vertical spacing max. The rebar must be centered in the core, not touching the sides — the grout must surround it completely to transfer load. Use rebar chairs or wire ties to hold rebar in position while you pour the grout.

Three steps. First, build the wall 4 courses high max — higher and the grout slumps as it pours. Second, place a grout stop at the bottom of the fill area (concrete footer or bond beam cap) so grout does not leak out under the course you are filling. Third, pour Quikrete Core Fill grout from the top, overfilling each core by about 1/2 in so grout settles and air bubbles rise. Vibrate gently with a rubber mallet against the wall every few cores to release trapped air. Do not pour a wall higher than 4 courses at once — pour, vibrate, let settle, add another course, repeat.

Yes — completely deduct them. A 6 × 4 ft window opening in a CMU wall removes 24 ft² of face area, which is 48 blocks per 8-ft wall section. That is about 48 × 0.104 ft³ = 5 ft³ of grout you do not need, or about 10 bags of Quikrete Core Fill. Doors and windows both fully skip core fill because you do not stack blocks there. Measure each opening as height × width and convert to block equivalents using the block count line on this page.