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United States

Concrete Block Calculator

Enter the length and height of your wall and the size of any doors or windows. You get the number of 8 × 8 × 16 in blocks, the bags of mortar to lay them and the grout to fill the cores, solid or only where the vertical bars go.

8 × 8 × 16 in concrete block (CMU)

Fill the cores with grout

"Every 32 in" means only the cells with a vertical bar every 32 inches. Your plans decide.

You need

– blocks

Mortar

QUIKRETE Mortar Mix #1102, data sheet Table 1: 80 lb = 12 standard 8×8×16 blocks, 60 lb = 9, 40 lb = 6

Link to this calculation Download estimate (PDF)

How to calculate concrete

  1. Measure the wall. Total length of all walls and the height, in feet.
  2. Take out the openings. Subtract the area of doors and windows in square feet.
  3. Count the blocks. An 8 × 16 in block with its mortar joint covers 8 × 16 = 128 sq in, so 144 ÷ 128 = 1.125 blocks per sq ft.
  4. Add extra. 5–10% for cuts, corners and breakage.
  5. Mortar and grout. Divide the blocks by the yield on the bag: 12 blocks per 80 lb bag of Quikrete Mortar Mix, about 3 blocks per 80 lb bag of Core-Fill Grout.

Worked example: a 20 ft wall, 4 ft high

  1. Area: 20 × 4 = 80 sq ft. Blocks: 80 × 1.125 = 90, plus 5% = 95 blocks.
  2. Mortar: 95 ÷ 12 blocks per 80 lb bag = 8 bags.
  3. Filling every core: 95 × 0.68 ÷ 3 = 21.5 cu ft = 32 bags of Core-Fill Grout.

Blocks, mortar and grout for common walls

Wall Sq ft Blocks Mortar 80 lb Core-fill 80 lb (solid)
10 × 4 ft 40 48 4 16
20 × 4 ft 80 95 8 32
20 × 6 ft 120 142 12 48
30 × 4 ft 120 142 12 48
40 × 4 ft 160 189 16 63
40 × 8 ft 320 378 32 126
100 × 4 ft 400 473 40 158

8 × 8 × 16 in blocks with 5% extra. Mortar: QUIKRETE Mortar Mix, 12 blocks per bag. Grout: QUIKRETE Core-Fill, 3 blocks per bag.

Frequently asked questions

How many concrete blocks per square foot?

1.125 standard 8 × 8 × 16 in blocks per square foot of wall, or 112.5 per 100 sq ft, before adding extra for cuts and breakage.

How much mortar do I need per block?

QUIKRETE's data sheet for Mortar Mix (#1102) gives 12 standard 8 × 8 × 16 blocks per 80 lb bag, 9 per 60 lb bag and 6 per 40 lb bag.

How much grout to fill block cores?

QUIKRETE Core-Fill Grout: an 80 lb bag yields about 0.68 cu ft and fills the cores of about 3 standard 8 in blocks, so roughly 0.23 cu ft per block. A cubic yard of grout fills about 119 blocks.

Do I need to fill every core?

Not always. Many walls are grouted only in the cells with vertical rebar, for example every 32 or 48 inches, plus bond beams. Retaining walls often need more. Your plans or local code decide; the calculator handles both.

Does the count include half blocks and corners?

It counts full blocks over the wall area. Corners, ends and cut blocks are covered by the extra percentage; raise it for walls with many corners or openings.