Concrete Block Calculator
Enter your wall size to get the blocks you need, plus an estimated cost. Waste is included.
Blocks needed
Estimated cost
How to calculate concrete blocks
A standard 8 by 16 inch block covers 0.89 sq ft, so you need 1.125 blocks per square foot. Find the wall area, multiply by 1.125, then add waste.
Formula: blocks = wall area (sq ft) × 1.125 × (1 + waste %), rounded up
Worked example: 20 ft × 8 ft wall
Wall area = 20 × 8 = 160 sq ft. Blocks: 160 × 1.125 = 180. Add 10% waste: 198 blocks.
Doors and windows
Measure the full wall, then subtract openings for an exact count. A door is about 20 sq ft and a window about 15 sq ft.
Common wall sizes
Cost tips
Prices on this page are editable estimates, not quotes. Get 2 to 3 local quotes before you buy, and ask if delivery is included. Delivery, tax and waste can change the total a lot. Order a little extra for cuts and breakage, and confirm final quantities with your supplier or a qualified professional.
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Frequently asked questions
How many concrete blocks do I need for a 20x8 wall?
A 20 ft by 8 ft wall needs 198 blocks with 10% waste, at 1.125 blocks per sq ft.
How big is a concrete block?
The standard block is 8 by 16 inches, which covers 0.89 sq ft, so you need 1.125 blocks per sq ft.
How much waste should I add?
Add 10% for straight walls and 15% for walls with many corners and openings.
Does this include mortar?
No, this counts blocks only. Use the mortar calculator for bags.
Are the prices accurate?
Prices are editable estimates. The defaults are typical US figures, and your local price can be higher or lower.