Free construction calculator
Block wall calculator
Wall size in, the number of blocks, courses and mortar bags out. Standard 8×8×16 CMU or half-high, with doors and windows taken out.
Result
| Wall area | 320 ft² |
|---|---|
| Blocks | 3781.125 per ft², plus the extra |
| Courses | 12About 30 blocks per course |
| Premixed mortar, 80 lb bags | 30About 13 standard blocks per bag |
- The mortar figure is a rule of thumb from common bag labels; your joints, your mixer and your crew change it.
- Corners, pilasters, bond beams and grout fill are extra. Rebar and grout follow your drawings.
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How it works
A standard 8×8×16 block covers 16 × 8 = 128 in² of wall with its mortar joint, which is 0.889 ft²: blocks = wall area ÷ 0.889 = 1.125 blocks per ft².
Take out the doors and windows, then add your extra for cuts and breakage (about 5%).
Courses: the wall height in inches ÷ 8. Mortar: common 80 lb bags of premixed mortar say they lay about 13 standard blocks, so the calculator divides the block count by 13.
Worked example
A wall 40 ft long and 8 ft high is 320 ft². 320 × 1.125 = 360 blocks; with 5% extra, 378 blocks.
That is 12 courses of 30 blocks each.
Mortar: 378 ÷ 13 is about 30 bags of 80 lb premixed mortar. Mixing your own from masonry cement and sand is cheaper on a wall this size; ask your supplier for the mix ratio of their cement.
Questions people ask
How many blocks are in 100 square feet?
112.5 standard 8×8×16 blocks, before waste.
How many blocks per bag of mortar?
About 13 standard blocks per 80 lb bag of premixed mortar, by the numbers on common bags. Your joint size and crew change it.
Does this include corner and bond beam blocks?
No. It counts the wall as plain stretchers. Swap the right number for corners, bond beams, lintels and pilasters from your drawings.
How do I count a wall with a footing step?
Run it once per section at its own height and add them up, or enter the average height for a rough number.
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Built by Northdesk
These calculators are made by Northdesk, construction business software with Dex, an AI assistant, built in.
- Masonry contractorsBlock, brick, stone and mortar on the right site, the saw and the mixer where they should be, and a crew that speaks two languages on the same page.
- Concrete contractorsPours that move with the weather, footings measured off the plans, finishers on the right site at 6 AM, and an inspector who signs in before you pour.
- AI estimating and takeoffDex reads your plans for quantities with the AI takeoff add-on, then drafts the estimate from your own prices, sections and wording.
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