Concrete Block Fill Calculator

Estimate grout volume and bags for the hollow blocks you plan to fill. Use a labeled block-supplier estimate or enter the fill volume specified for your actual units.

Number of blocks to fillblocksCount only the blocks whose cores will be filled. This is not the number of blocks to buy.

Block fill-volume exampleNominal thickness alone does not determine cavity volume. Presets are approximate supplier examples.

Fill volumeyd³ / 100 blocksThe rate below is used directly; edit it for your block design. Presets assume hollow blocks filled with grout.

Fill-volume unitsChanging units converts the entered rate.

Additional grout volumeft³Add separately measured bond-beam, pilaster or other void volume only if it is not already included in the chosen fill rate.

Additional-volume units

Extra material allowance%An editable purchasing buffer, not a design requirement. Avoid adding waste twice if your supplier rate already includes it.

Mixed grout yield per bagft³/bagExample: 80-lb Amerimix AMX 610 FG lists approximately 0.57 ft³. Check your own grout product; concrete and mortar yields differ.

Bag-yield units

Price per bag (optional)your currencyMaterial cost only. Enter a local price or leave 0 to omit cost.

Calculation results

Estimated material

—

How to use this calculator

Count the filled units

Use the number of hollow blocks to be grouted, not your spare blocks or the entire wall if only selected units are filled.

Choose the correct fill volume

Use your block supplier’s cavity or grout estimate when available. The four presets are examples from Tidewater, not universal values for every block with the same nominal thickness.

Add only missing volume

Include additional grout spaces not already covered by the base estimate. For partial cells, use a project-specific takeoff or custom rate rather than assuming that every unit is fully grouted.

Set the grout yield

Enter the mixed yield of the grout you will purchase and your allowance. The tool rounds the project total up once to whole bags.

Formula and worked example

Core grout = number of filled blocks × fill volume per block
Base volume = core grout + separately measured additional volume
Order volume = base volume × (1 + allowance ÷ 100)
Bags = round up(order volume ÷ mixed grout yield per bag)

For 100 blocks at 0.93 yd³ per 100 blocks, the base grout estimate is 0.93 yd³, or 25.11 ft³. With no additional volume and a 10% allowance, order volume is 1.023 yd³, or 27.621 ft³. At 0.57 ft³ per bag, 27.621 ÷ 0.57 = 48.4579 bags, rounded up to 49. These inputs combine an illustrative block estimate and an illustrative grout yield; they do not approve the products for a particular wall.

Illustrative hollow-block fill volumes

Tidewater Block rule-of-thumb estimates. No calculator allowance is included in this table; actual unit geometry and the grouting layout can differ.
Nominal block thickness	Grout per 100 blocks	Equivalent per block
6 in	0.63 yd³	0.1701 ft³
8 in	0.93 yd³	0.2511 ft³
10 in	1.22 yd³	0.3294 ft³
12 in	1.44 yd³	0.3888 ft³

Frequently asked questions

Is this the same as a concrete block calculator?

No. A block-count calculator estimates how many units build a wall. This tool starts with the units to be filled and estimates grout inside their voids. It does not estimate laying mortar or the concrete in the block shells.

Can I fill the blocks with ordinary concrete?

This quantity tool does not choose a fill material. Use the grout or other material specified for the masonry system. Aggregate size, flow and the approved wall design matter; concrete, grout and mortar are not automatically interchangeable.

Why can two block-fill calculators disagree?

They may use different cavity volumes, unit designs, filled-cell layouts, extra-volume allowances or bag yields. Compare the underlying volume per block before comparing the final number of bags.

Does it account for rebar and partially filled cells?

Not automatically. The presets are general fill-volume estimates. Use a supplier or design takeoff for selected cells, reinforcement and special blocks, and avoid double-counting any extra grout volume.

Are the defaults structural recommendations?

No. The calculator estimates quantities only. Whether a wall should be grouted, which cells are filled, the grout specification and reinforcement must come from the project requirements.

Methodology and sources

The presets are approximate hollow-block grout quantities, not solid external block volumes. The tool does not design a wall, choose reinforcement, specify grout placement or establish code compliance. Costs exclude blocks, laying mortar, reinforcement, pumping, labor and tax. Use project-specific dimensions and approved materials before ordering.

Tidewater Block — estimating guide — Source of the four block-fill volume examples; the guide labels them rule-of-thumb estimates.
Amerimix AMX 610 FG — July 2026 technical sheet — Source of the example mixed yield of 0.57 ft³ per 80-lb bag. This yield excludes waste.
NIST Handbook 44 — measurement tables — Volume-unit definitions and conversions.

Sources checked September 1, 2026. Referenced organizations do not endorse Efficienco. Calculations retain full precision until display; purchase units round up.