Concrete Block Calculator
Count the CMU blocks, mortar and fill needed for a block wall.
What you'll need to order
- 8x8x16 CMU block
- type S mortar
- rebar
- grout
- wall ties
Prices vary by region and haul distance. Get quotes from at least two local suppliers.
How this calculator works
blocks = (length × height − openings) × 1.125 × 1.05
A nominal 8 by 8 by 16 inch block, including its mortar joint, covers 0.888 sq ft — so 1.125 blocks per square foot. Actual block dimensions are 3/8 inch smaller in each direction to allow for the joint.
Worked example
With wall length 20 ft, wall height 8 ft, openings to deduct 0 sq ft, this calculator returns 189 .
Waste allowance
The headline figure includes a 5% allowance for waste and over-ordering. The exact requirement is shown alongside it.
Blocks needed by wall height
Figures below assume wall length 40 ft × openings to deduct 0 sq ft. Change any measurement in the calculator to get your own numbers.
| Wall height | Blocks needed | Mortar bags (70 lb) (bags) | Core fill if fully grouted (cu yd) |
|---|---|---|---|
| 2 ft | 94.50 | 3.38 | 2.63 |
| 4 ft | 189.0 | 6.75 | 5.25 |
| 6 ft | 283.5 | 10.13 | 7.88 |
| 8 ft | 378.0 | 13.50 | 10.51 |
| 10 ft | 472.5 | 16.88 | 13.14 |
| 12 ft | 567.0 | 20.25 | 15.76 |
A 40 ft wall with no openings, including a 5% breakage allowance. Standard 8x8x16 in CMU.
How many blocks for a wall, foundation or garage?
| Job | Size | Blocks needed | Material cost |
|---|---|---|---|
| Garden retaining wall | 30 ft × 3 ft × 0 sq ft | 106.3 | $957 – $1,914 |
| Basement wall run | 40 ft × 8 ft × 20 sq ft | 354.4 | $3,189 – $6,379 |
| Single garage, one side | 22 ft × 9 ft × 0 sq ft | 233.9 | $2,105 – $4,210 |
| Full garage perimeter | 92 ft × 9 ft × 130 sq ft | 824.5 | $7,421 – $14,841 |
| Boundary wall | 100 ft × 6 ft × 0 sq ft | 708.8 | $6,379 – $12,758 |
Openings are the total square footage of doors and windows. Subtracting them matters — a single garage door is 130 sq ft, or nearly 150 blocks.
Cost range uses $9–$18 per block installed for material only.
What does a concrete block wall cost?
Material typically runs $9 to $18 per block installed. Installed, including mortar and labour. The blocks themselves are only $1.50 to $3 each — this is a labour-dominated trade.
What moves the price:
- Whether cores are grouted and reinforced, which most structural walls require
- Footing preparation, priced separately and often as much as the wall
- Block type — standard grey CMU against split-face or architectural units
- Wall height, since anything above about 8 ft needs scaffolding
Prices are US averages and move with fuel, season and haul distance. Always get two local quotes before budgeting.
Block sizes and how many per square foot
| Type | Blocks per sq ft | Notes |
|---|---|---|
| 8x8x16 in standard CMU | 1.13 | The default; what this calculator assumes |
| 4x8x16 in half-height | 2.25 | Veneer and low garden walls |
| 12x8x16 in | 1.13 | Same face size, thicker wall |
| 6x8x16 in | 1.13 | Non-structural partitions |
| 8x4x16 in solid cap | 2.25 | Sold by the linear foot for wall caps |
Face size drives the count, not thickness. A 12 inch block covers the same wall area as an 8 inch one — it just costs more and weighs more.
Frequently asked questions
How many concrete blocks do I need?
Multiply wall area in square feet by 1.125, then add 5% for breakage. A 40 by 8 ft wall is 320 sq ft, which needs about 378 blocks.
How much does a concrete block wall cost per square foot?
$10 to $20 per square foot installed, including mortar, labour and standard reinforcement. Footings and grouting are usually quoted separately.
How many blocks can one person lay in a day?
An experienced mason lays 150 to 200 standard blocks a day on a straight run, considerably fewer around corners, openings and reinforcement.
How many blocks per square foot?
One and an eighth, for standard 8 by 8 by 16 inch CMU. A quick field check: 112 or 113 blocks per 100 square feet of wall.
How many blocks does a bag of mortar lay?
About 28 blocks per 70 lb bag of type S mortar. Block takes less mortar per square foot than brick because there are far fewer joints.
Do concrete block walls need to be filled with grout?
Not always. Non-structural walls can stay hollow. Retaining walls, walls with rebar, and anything carrying load need the reinforced cells grouted solid — typically every 32 or 48 inches, not the whole wall.
What mortar type is right for block?
Type S for most block work, including foundations and retaining walls, because of its higher compressive and bond strength. Type N is acceptable for non-load-bearing partitions above grade.