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.
Switch the site to metric — the control is in the footer — and your inputs, your results and the tables below follow. The formula, the constants, the guidance text and the sources stay in US units on purpose: that is how the standards they come from are written, and restating them would detach each figure from the document you are meant to be able to check it against.
Where these numbers come from
- ASTM C90 (Loadbearing Concrete Masonry Units) 2023 — nominal and actual dimensions of concrete masonry units, from which 1.125 blocks per sq ft follows
The edition matters as much as the number. Jurisdictions adopt code revisions on their own schedule, so verify which one applies where you are building.
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. Open any row to load it into the calculator above — the link carries the numbers with it, so it can go straight to a supplier or a crew.
| 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?
Open any row to load it into the calculator above — the link carries the numbers with it, so it can go straight to a supplier or a crew.
| 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.