Concrete Block Fill Calculator
Calculate concrete or mortar volume needed to fill hollow concrete blocks and cinder blocks
Calculate Concrete Block Fill Requirements
Width or length of the wall to be filled
Height of the wall to be filled
Block Specifications
Number of concrete webs in the block
Thickness of outer walls
Thickness of internal webs
Account for spillage and overfill (5-10% recommended)
Concrete Block Fill Requirements
Block dimensions: 16.0" × 8.0" × 8.0"
Fill volume without waste: 0.000 cubic yards
With 5% wastage: 0.000 cubic yards
Inside dimensions per block: 12.3" × 5.5" × 8.0"
Fill Analysis
Example Calculation
Retaining Wall Fill Project
Project: 3.0 m wide × 2.4 m high retaining wall
Wall area: 3.0 × 2.4 = 7.2 square meters (77.5 sq ft)
Block size: Standard 8" × 16" × 8" block
Block area: 8" × 16" = 128 sq in (0.89 sq ft)
Blocks needed: 77.5 ÷ 0.89 = 87 blocks
Core volume per block: 392 cubic inches
Total fill volume: 392 × 87 = 34,104 cubic inches
In cubic yards: 34,104 ÷ 46,656 = 0.73 cubic yards
Material Requirements
Base fill volume: 0.73 cubic yards
With 5% wastage: 0.73 × 1.05 = 0.77 cubic yards
Concrete bags needed: ~29 bags (60 lb bags)
Recommendation: Use concrete with aggregate for structural strength
Typical Core Volumes
Standard 8" blocks are most commonly filled
Fill Materials
Concrete
High strength, structural
With rebar reinforcement
Mortar
Standard strength
Non-structural applications
Grout
Fine aggregate
Easier to pour
Fill Tips
Add 5-10% extra for wastage and overfill
Use vibration to eliminate air pockets
Fill cores with rebar before pouring
Pour continuously to avoid cold joints
Use proper concrete mix for strength
Understanding Concrete Block Fill Calculations
Why Fill Concrete Blocks?
Filling hollow concrete blocks with concrete or mortar significantly increases the structural strength of the wall and provides better resistance to lateral forces. It also allows for proper rebar placement and creates column-like structures throughout the wall.
Core Volume Calculation
- •Subtract shell thickness from block width and thickness
- •Subtract web thickness for internal webs
- •Multiply inside dimensions by full block height
- •Account for number of cores per block
Fill Material Options
Concrete Fill:
- • Maximum structural strength
- • Compatible with rebar reinforcement
- • Use 3000+ PSI mix for load-bearing walls
- • Add aggregate for better strength
Mortar Fill:
- • Lower strength than concrete
- • Easier to work with and pour
- • Suitable for non-structural applications
- • Less expensive than concrete