Concrete Block Fill Calculator

Concrete Block Fill Calculator for Hollow CMU Cores

The Concrete Block Fill Calculator estimates how much concrete or mortar fills the hollow cores of CMU blocks in a wall. Filling cores with rebar strengthens load-bearing and reinforced block walls.

Core volume per block

Core volume depends on block length, face height, wall thickness, shell thickness, and web count:

$$V_{core} = W_{inside} \times H_{inside} \times T_{block}$$

where $W_{inside}$ is inside width along the block length, $H_{inside}$ is inside depth on the face, and $T_{block}$ is block thickness into the wall.

Total fill volume

Multiply core volume per block by the number of blocks in the wall, then add a wastage allowance of 5% to 10% for spillage and overfill.

Frequently Asked Questions

Should concrete blocks be filled?

Filling cores with concrete and rebar increases wall strength, especially for load-bearing walls, high walls, and seismic zones. Non-structural garden walls may not need fill.

How much concrete fills an 8 by 8 by 16 inch block?

A typical 6 inch thick block has about 392 to 550 cubic inches of core volume depending on shell and web dimensions. Use this calculator with your exact block specs.

How do I calculate fill volume for a whole wall?

Find core volume per block, count blocks from wall area divided by block face area, then multiply. Add 5% to 10% wastage for the final order.

Can I use mortar instead of concrete for block fill?

Mortar can fill small voids, but structural core fill should use grout or concrete for strength and flow around rebar. Match the fill material to your engineering requirements.

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Concrete Block Fill Calculator