Find out how many concrete blocks and how much mortar you need for a wall. Enter the wall size and your block size to get a count.
0blocks
| Item | Amount |
|---|---|
| Wall area (after openings) | |
| Blocks per square foot | |
| Courses (rows) high | |
| Blocks per course | |
| Mortar needed | |
| Mortar bags (80 lb) |
Each block takes up its own size plus one mortar joint. The calculator finds how many of those fit in one square foot of wall and multiplies by your wall area. Enter your block's actual length and height, and the joint width.
Blocks per sq ft = 144 ÷ ((block length + joint) × (block height + joint))
Blocks = wall area × blocks per sq ft × (1 + waste), rounded up
A standard 8 x 8 x 16 inch block is really about 15 5/8 inches long and 7 5/8 inches high, so with a 3/8 inch joint it covers a 16 x 8 inch space. That gives 1.125 blocks per square foot. Thickness (4, 6, 8, 10, or 12 inch) doesn't change the count.
The calculator works for any wall made of blocks in a regular grid, including retaining wall blocks. Choose Custom, enter the block's face length and height, and set the joint to 0 for dry-stacked blocks. It counts blocks only. See the note below on what is not included.
The tool also shows how many courses (rows) and blocks per course the full wall has, which is useful when laying out the wall.
The mortar estimate assumes standard face-shell bedding, where mortar is placed only on the outer edges of each block, and a 3/8 inch joint. It adds 25 percent for waste and assumes an 80 lb bag yields about 0.6 cubic feet. Treat it as a rough guide and check your bag's label.
With standard 8 x 8 x 16 inch blocks and a 3/8 inch joint, you need 1.125 blocks per square foot of wall. Other sizes change that number, so use the calculator.
A 120 square foot wall needs 135 blocks, or about 142 with 5 percent extra.
A rough guide is one 80 lb bag of mortar for every 35 to 40 blocks, depending on joint size and technique. The calculator gives an estimate for your wall.
Many garden and landscape walls are laid dry-stacked or with mortar only. Taller walls, retaining walls, and structural walls usually need rebar and grout in some or all of the cores. Follow your plans and local code.
It is a general block wall calculator. It will count the blocks for a retaining wall if you enter the block's size and set the joint to 0, but it doesn't calculate the gravel base, backfill, drainage pipe, or geogrid that a retaining wall needs. For that, use the retaining wall calculator.
Choose Custom and enter your block's actual length and height in inches, plus your joint width. Measure the block itself, since many are slightly smaller than their nominal size.
No, bricks are smaller. Use the brick calculator for those.