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Calculate CMU blocks needed for walls. Enter wall length, height, and block size to get block count with 5% waste for masonry and construction projects.
Free concrete calculator for slabs, footings, and pours. Enter length, width, depth to get cubic yards, cubic feet, and bag counts with waste factor.
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Industry rule of thumb: approximately 7–8 cu ft of mortar per 100 sq ft of wall area with standard 3/8″ bed joints for CMU block.
Mortar (cu ft) ≈ Wall Area (sq ft) × 0.08Scale mortar volume proportionally when joint thickness differs from the 3/8″ baseline. Thicker joints increase mortar consumption significantly.
Adjusted Volume = Base Volume × (Joint Thickness ÷ 0.375)An 80 lb bag of Type S or N masonry premix yields roughly 0.75 cu ft when mixed. Round up to whole bags and add 10% for waste.
Bags = ceil(Mortar Volume ÷ 0.75)Updated: July 2026
A 40×5 ft block wall (200 sq ft) at 3/8″ joints needs about 16 cu ft of mortar — roughly 22 bags of 80 lb premix or 6 field-mixed batches.
Brick walls consume more mortar per sq ft than block due to smaller units. Use wall area and verify against brick supplier tables for thin joints.
Repointing existing joints on 30 sq ft of aging brick facade requires less total mortar but benefits from small-batch mixing to match color and consistency.
Calculate how much mortar you need for concrete block, brick, or stone masonry walls before starting a project. Enter wall area and joint thickness to estimate mortar volume, number of 80 lb premix bags, or batches for a 1:3 cement-sand field mix.