Free estimate — verify against local code before building
Concrete Block Fill Calculator
Turn a wall area or block count into editable core-fill volume, grout bags, and optional cost.
What this calculator includes
Estimate grout for concrete masonry unit cores from measured wall area or a known block count. Choose the nominal block width, confirm the editable cells-per-block assumption, enter the percentage of vertical cells represented by the approved fill schedule, and verify the visible per-cell volume and bag yield before ordering.
Next step in your project
Complete the masonry-wall material takeoff
Carry the wall dimensions into a mortar estimate, then choose the masonry unit, joint profile, bag yield, waste, and optional bag price.
Open Mortar Calculator →Compatible measurements are carried into the next calculator; product-specific assumptions remain editable.
How to use this concrete block fill calculator
- 01
Choose the measurement method
Enter wall length, height, and openings for an early block count, or use the known block count from a completed masonry takeoff.
- 02
Use the approved fill schedule
Enter the share of the wall represented by filled cells or units. The calculator does not decide which cells require grout.
- 03
Verify cells and volume
Confirm cells per block and replace the nominal-width per-cell default with the unit manufacturer's published grout volume for the exact block shape and web configuration.
- 04
Confirm the purchase yield
Use the bag label or ready-mix supplier requirements, then add an allowance appropriate for spillage, consolidation, and field conditions.
Worked example
Example: 30 ft by 8 ft wall with half the cells represented
A 240 sq ft wall contains about 270 nominal 8-by-16 modules. At two cells per block and 50% represented fill, that is 270 filled-cell equivalents. Using the editable 0.126 ft³ per-cell start (an 80 lb grout bag fills both cores of roughly 2.7 standard 8 in blocks) and 10% waste gives about 37.4 ft³, or 1.39 yd³, before supplier rounding.
Practical buying and overage guidance
Confirm the exact CMU manufacturer and shape, approved grout specification, filled-cell schedule, reinforcement, cleanout and lift requirements, pump or placement access, bag yield or supplier minimum, and compatible batch size before purchasing.
Continue the project
Pour a Concrete Slab
Plan slab excavation, base, concrete yards or bags, forms, reinforcement allowances, delivery, labor, equipment, and contractor pricing.
Open the project workflow →Calculation sources and review
Primary references and formula assumptions are linked so you can verify them against the selected product, supplier, and adopted local requirements.
Internal formula review completed July 13, 2026. What this review covers
- CMHA TEK 04-02A — Estimating Concrete Masonry Materials (opens in a new tab)
Table 4 provides the editable starting grout volumes for vertical cores in nominal 6, 8, 10, and 12 inch CMU.
- CMHA TEK 09-04A — Grout for Concrete Masonry (opens in a new tab)
Masonry grout selection and placement context.
- QUIKRETE Core-Fill Grout Fine product data (opens in a new tab)
Published 0.68 ft³ yield for the editable 80 lb bag starting value.
Frequently asked questions
How much grout fits in an 8-inch concrete block?
Core volume varies by manufacturer, unit shape, and webs. The calculator starts from CMHA vertical-core guidance, assumes two cells per common unit, and keeps both cells per block and volume per cell editable so exact product data can replace them.
Should I fill every block core?
Not automatically. Filled cells, reinforcement, grout type, cleanouts, lifts, and inspection come from the approved masonry design and local requirements.
Why does wall area only estimate the block count?
The wall method assumes the common 8-by-16-inch nominal face module. Bond pattern, cuts, bond beams, special units, openings, and waste can change the actual unit count.
Can I use ordinary concrete in CMU cores?
Use the grout or fill specified for the masonry assembly. Aggregate size, flow, consolidation, lift height, and placement requirements differ from a general concrete order.
How much extra grout should I order?
The appropriate allowance depends on unit tolerances, cell cleanliness, placement method, lift plan, spillage, and supplier rounding. Edit the waste field using project and supplier guidance.