Concrete block calculator
Enter the wall size. Standard blocks have a nominal face of 8 × 16 in, so it takes 1.125 blocks per square foot: a 20 ft long, 4 ft high wall needs 90 blocks before extra.
Blocks
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Wall area
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How the calculator works
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Block sizes are given as nominal dimensions, which include a 3/8 in mortar joint. A standard block is actually about 7⅝ × 15⅝ in, and with mortar it fills 8 × 16 in (0.889 sq ft) of wall. Dividing the wall area by that face area gives the number of blocks.
Blocks per square foot
| Nominal face | Face area | Blocks per sq ft |
|---|---|---|
| 8 × 16 in | 0.889 sq ft | 1.125 |
| 4 × 16 in | 0.444 sq ft | 2.25 |
Block thickness (6, 8, 10 or 12 in) does not change the count; it changes the weight, the mortar and the fill.
Before you build
Retaining walls and load-bearing walls need footings, reinforcement and often an engineer's design; local codes set the rules. Count corner and end blocks separately if your supplier sells them as special units.