Block Wall Calculator
Find how many concrete blocks you need for a wall, how many courses high it runs, and how many bags of mortar to lay them.
- Wall area
- Per square foot
- Net count
- Courses
- Mortar
- Mortar volume
- Cost
- Add prices to estimate
Wall List
Walls you add are saved in this browser.
| Wall | Size | Area | Blocks | Mortar Bags | Cost | Remove |
|---|
How to Calculate Concrete Blocks
Concrete blocks are named by their nominal size, which includes a 3/8″ mortar joint. A standard 8×8×16 block is actually 7⅝″ × 7⅝″ × 15⅝″, so with mortar it covers 8″ × 16″ of wall. That is 128 square inches, and 144 ÷ 128 = 1.125 blocks per square foot. Blocks 4″, 6″ and 12″ thick have the same 8″ × 16″ face, so they cover the same area.
Multiply the wall area by the blocks per square foot, subtract doors and windows, and add a few percent for cuts and breakage.
Worked Example
Common Block Sizes
| Type | Actual Size (D × H × L) | Per Sq. Ft. | Per 100 Sq. Ft. |
|---|
With 3/8″ mortar joints, before waste.
Mortar
Quikrete's data sheet says an 80 lb bag of its Mortar Mix lays up to 13 standard 8×8×16 blocks, so the calculator divides the block count by 13 and rounds up. The mortar volume assumes full bed and head joints; laying mortar only on the face shells, as masons often do, uses less.
Tips for Block Walls
Plan wall lengths in multiples of 8″ and heights in multiples of 8″ to cut fewer blocks. Order corner and half blocks for ends and openings. Walls that hold back soil or carry a load need footings, reinforcing steel and grouted cores designed for the job; check local code.