Concrete Block Calculator
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- Materials
- Labor
- Profit
Rebar, grout for filled cores and footing concrete are extra. Use the rebar and concrete calculators for those.
Turn this into a quote
A one-page PDF for your customer, filled in from the numbers above. Your markup isn't shown.
How the concrete block calculation works
Wall area = length × height − openings
A 40 ft wall, 4 ft high, with no openings is 160 sq ft.
Blocks = area × blocks per sq ft
A standard 8 × 8 × 16 in block covers 0.889 sq ft with the joint, so you need 1.125 per sq ft: 160 × 1.125 = 180 blocks.
Add waste and round up
5% covers cuts and breakage. 180 becomes 189 blocks.
Mortar bags = blocks ÷ blocks per bag
QUIKRETE rates an 80 lb bag of Mason Mix at up to 13 standard blocks, so 189 blocks need 15 bags. "Up to" is a best case: thick joints or a full mortar bed use more, so round up or add a spare bag.
Price it with labor and markup
Add mason hours at your cost per hour, then apply markup to materials plus labor.
Worked example. A 40 × 4 ft wall is 160 sq ft. At 1.125 blocks per sq ft plus 5% waste you need 189 blocks ($425.25 at $2.25) and 15 bags of mortar ($135). With 16 labor hours at $60 the cost is $1,520.25, and a 25% markup prices the wall at $1,900.31.
Concrete Block FAQ
How many concrete blocks do I need for a wall?
Multiply the wall area in sq ft by 1.125 for standard 8 × 16 in block, then add about 5% for waste. A 160 sq ft wall needs 189 blocks.
How many cinder blocks are in a square foot?
1.125 standard 8 × 8 × 16 in blocks per sq ft, because each block's face with mortar joint is 16 × 8 in, or 0.889 sq ft.
How much mortar do I need for concrete block?
QUIKRETE's data sheet rates one 80 lb bag of Mason Mix at up to 13 standard 8 × 8 × 16 in blocks. Treat that as a best case and use the yield printed on the bag you buy. Enter it and the calculator rounds bags up.
How much does a concrete block wall cost?
Add blocks, mortar, labor and your markup. The default 160 sq ft wall comes to about $11.88 per sq ft at a 25% markup.
How many cinder blocks do I need for a 10 × 10 ft wall?
A 10 × 10 ft wall is 100 sq ft. At 1.125 blocks per sq ft that is 112.5, so 113 blocks with no waste, or 119 blocks with 5% for cuts and breakage. Subtract any door or window openings first.
Is a cinder block the same as a concrete block or CMU?
In everyday use, yes. Builders and suppliers call the standard hollow block a concrete masonry unit (CMU). The 8 × 8 × 16 in size is nominal: the block itself is slightly smaller, and the mortar joint makes up the rest, which is why 1.125 blocks cover a square foot.
Should I fill the block cores with concrete?
Retaining and load-bearing walls usually need rebar and grouted cores where the engineer or code requires it. Price grout with the concrete calculator.
Sources: QUIKRETE: Mason Mix data sheet (yield per 80 lb bag)