How Many Blocks to Build a Wall? Formula

To build a wall with standard 8x8x16 concrete block, multiply the wall's length by its height in feet to get the area, then multiply by 1.125, since one block with a 3/8 inch mortar joint covers 0.889 square feet of wall face. Below is the block count by wall size, how many mortar bags and dollars that adds up to, and how the total compares to bricks or a poured concrete wall.

The formula: multiply wall area by 1.125

A standard concrete block, or CMU, presents an 8 inch high by 16 inch long face to the wall. With a 3/8 inch mortar joint it takes up a modular 0.889 square feet of wall area, so flip that fraction over and one square foot of wall needs 1.125 blocks.

The full calculation is two steps: find the wall area in square feet, then multiply by 1.125 to get the raw block count before waste.

Wall area (ft2) = Length(ft) x Height(ft)Blocks = Wall area x 1.125 x (1 + Waste% ÷ 100)

Always round the final number up to a whole block, and add 5 to 10% for waste to cover breakage, cuts, and corners. For the exact count on your own dimensions, including courses and blocks per course, run the numbers through the concrete block calculator.

How many blocks to build a wall, by size

These figures use standard 8x8x16 block, a 3/8 inch joint, and a 10% waste allowance for corners and breakage.

Wall (L x H)	Area (sq ft)	Blocks (+10%)	Mortar bags (80 lb)
8 x 8 ft	64	80	7
10 x 8 ft	80	99	9
20 x 6 ft	120	149	13
25 x 8 ft	200	248	21
40 x 8 ft	320	396	33

Every wall is different once doors, windows, and corners enter the picture, so treat this table as a starting budget rather than a final order.

Mortar, cement, and other materials needed for a wall

Block is only one line item. Budget about 8 to 10 bags of pre-mixed 80 lb mortar per 100 blocks, or roughly 3 bags of masonry cement mixed with about 0.4 cubic yards of sand for the same 100 blocks.

That works out to about one 80 lb bag of pre-mixed mortar per 12 blocks at a standard 3/8 inch joint. Wider joints, or full bedding instead of face-shell bedding, push the bag count up.

For the full breakdown by bag size, including 60 lb and 40 lb options and the sand ratio for masonry cement, see how many bags of mortar per 100 block.

If the wall is loadbearing or a foundation, plan on rebar dropped into the cores and grout to fill them, a separate material total from the block and mortar count.

Openings, corners, and waste: what changes the total

Subtract door and window openings from the wall area before multiplying by 1.125, never after. A 3 by 7 foot door opening removes 21 square feet, worth about 24 blocks, from the order.

Corners do not add extra blocks on a straight run since half blocks simply alternate the bond, but an L shaped or stepped wall should be split into straight sections, calculated separately, then added together.

A 5% waste factor suits a simple rectangular wall with clean cuts. Bump it to 10% for walls with many corners, openings, or a crew still learning to lay block.

Stacked pallets of concrete block and bags of mortar staged beside a half-built wall on a job site

Cinder blocks vs a poured concrete wall: cost per square foot

State the approved wall dimensions, block, reinforcement, foundation and finish in each quote.

Labor costs shift the other way: block walls take longer to lay and mortar than a form-and-pour wall, but block is far easier for a DIY crew to tackle one section at a time.

Blocks vs bricks for the same wall

Concrete block and brick are not interchangeable one for one. A standard modular brick, with its 2 2/3 by 8 inch face and a 3/8 inch joint, covers only about 0.148 square feet, compared to 0.889 square feet for a single concrete block.

That means a wall needs roughly 6 to 7 bricks for every 1 concrete block covering the same area. A 10 by 10 foot wall, 100 square feet, takes about 113 concrete blocks but closer to 675 to 700 standard bricks for a single wythe.

Price brick and block only after the wall assembly, foundation, reinforcement, finish and labor scope are defined. If your project needs the block side worked out with openings and waste, see how many concrete blocks do I need.

By Calcnaut

Formula and declared-case checks run during the build; sources are listed for readers to review. Read our method and editorial policy.

Frequently asked questions

How many blocks do I need to build a 10x10 wall?

A 10 by 10 foot wall is 100 square feet, which needs about 113 standard 8x8x16 blocks before waste, or roughly 124 with a 10% waste allowance for corners and cuts.

How do I price an order of 1,000 concrete blocks?

Multiply 1,000 by the supplier's current price for the exact unit, then include pallet deposits, delivery, tax, breakage allowance and return terms. This is a material-order total, not the installed wall cost; mortar, footing, reinforcement, grout, finish and labor are separate.

How should I compare a poured wall with a block wall?

Compare approved systems serving the same loads and function. State dimensions, foundations, reinforcement, concrete or masonry units, grout, drainage, finish, access and labor for both options; the unit-count calculator cannot determine which wall system is appropriate.

How many bricks for a 10x10 wall?

A 10 by 10 foot single-wythe brick wall needs about 675 to 700 standard modular bricks, since each brick covers only about 0.148 square feet compared to 0.889 square feet for one concrete block.

How much wall face can 5,000 standard blocks cover?

At 1.125 standard 8x8x16 blocks per square foot, 5,000 blocks cover about 4,444 square feet of uninterrupted wall face before waste. Actual building quantities require plans for wall lengths, heights, openings, corners, partitions, bond and project-specific waste.

Sources and references

These references and structured source records support the method and material data used on this page.

How Many Blocks to Build a Wall?

Key takeaways