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Blocks for a 20 × 6 ft wall
A 20 ft long, 6 ft high wall is 120 square feet. With standard 8 × 8 × 16 inch blocks you need about 149 blocks including 10% waste.
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Estimate only. Bag yields, material density and waste vary by product and supplier. Confirm quantities with your supplier and check local building codes before you buy or build.
How many blocks for a 20 × 6 wall?
One 8 × 16 inch block face (with the mortar joint) covers 0.89 square feet, so it takes 1.125 blocks per square foot. 120 square feet × 1.125 = 135 blocks, or 149 with 10% extra for breakage and cuts.
Courses and mortar
At 8 inches per course a 6 ft wall is 9 courses high, each about 15 blocks long. Plan on about 3 bags of 80 lb mortar mix per 100 blocks: 5 bags for this wall.
Footing and reinforcement
Block walls need a concrete footing below the frost line, and taller or retaining walls usually need rebar and grouted cores. Check local building codes; walls over about 4 ft often need an engineered design.
Frequently asked questions
How many cinder blocks for a 20 ft by 6 ft wall?
About 149 standard 8×8×16 blocks with 10% waste.
How much mortar for a 20 × 6 wall?
About 5 bags of 80 lb mortar mix.
How accurate is this estimate?
It is a planning estimate, not an order. Bag yields, material density and waste vary by product, supplier and job, so confirm quantities with your supplier and check local building codes before you buy or pour.
Are my measurements saved?
No. Everything is calculated in your browser. Nothing is uploaded or stored.
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Also on this topic: Concrete block calculator, Retaining wall cost.
Common sizes: 20 × 4 ft wall, 30 × 4 ft wall, 50 × 4 ft wall, 40 × 6 ft wall, 100 × 6 ft wall, 20 × 8 ft wall.