How to use the concrete block calculator
- Enter the wall length and height. For a building, add up the lengths of every wall. Subtract the area of doors and windows in the openings field.
- Pick the block size. The first number is the wall thickness. Standard US blocks are 8″ high and 16″ long including the mortar joint, whatever the thickness.
- Choose the core grout if the wall is reinforced. Vertical rebar is set in a grouted core at the spacing your plans call for.
- Add the price per block for a cost estimate.
How many concrete blocks per square foot?
A standard block is 7⅝″ × 15⅝″ on its face. With a ⅜″ mortar joint, each one covers a nominal 8″ × 16″, or 0.889 sq ft. That makes 1.125 blocks per square foot of wall, or 112.5 blocks per 100 sq ft.
Blocks = Wall area × 1.125 × (1 + Waste)
Courses = Height ÷ 8″
Mortar ≈ 8.5 ft³ per 100 blocks (face-shell bedding)
Core grout = Blocks × core volume × share of cores filled
Metric UK blocks are 440 × 215 mm with 10 mm joints, so each covers 450 × 225 mm, or 9.88 blocks per m².
Mortar and grout estimates
Mortar use depends on joint width and how much the mason butters the webs, so published figures vary. We use the common estimate of about 8.5 ft³ of mortar per 100 blocks laid with face-shell bedding, which works out to roughly 2½ bags of 70 lb masonry cement per 100 blocks when mixed with sand at 1:3. Premixed 80 lb mortar mix covers far fewer blocks per bag, so check the yield on the bag you buy.
An 8″ hollow block has about 0.25 ft³ of open core, so a fully grouted 8″ wall uses about 0.9 to 1 cubic yard of grout per 100 blocks. With rebar every 48″ only one core in six is filled.
| Block | Blocks per 100 ft² | Core volume per block | Grout, fully grouted, per 100 blocks |
|---|---|---|---|
| 6×8×16″ | 112.5 | ≈ 0.17 ft³ | ≈ 0.63 yd³ |
| 8×8×16″ | 112.5 | ≈ 0.25 ft³ | ≈ 0.93 yd³ |
| 10×8×16″ | 112.5 | ≈ 0.32 ft³ | ≈ 1.19 yd³ |
| 12×8×16″ | 112.5 | ≈ 0.39 ft³ | ≈ 1.44 yd³ |
Worked examples
A 40 ft long, 4 ft high wall of 8″ block: 160 ft² × 1.125 = 180 blocks, plus 5% = 189 blocks in 6 courses. Mortar: about 16 ft³, or 5 bags of masonry cement.
Walls totalling 88 ft, 8 ft high, with a 16 × 7 ft door and 2 windows of 12 ft²: 704 − 112 − 24 = 568 ft² → 639 blocks, plus 5% = 671 blocks. With rebar every 48″, grout ≈ 671 × 0.25 ÷ 6 = 28 ft³, about 1.04 yd³.
Frequently asked questions
How many blocks are in a pallet?
It varies by supplier and size. A pallet of 8×8×16 blocks commonly holds 90 to 108 blocks. Ask your yard, as delivery is often priced per pallet.
How much does a concrete block wall cost?
Standard 8″ blocks cost around $2 to $4 each in the US, so block alone runs roughly $2.50 to $4.50 per square foot of wall. Mortar, grout, rebar and footing are extra, and labor often costs more than materials.
Are cinder blocks and concrete blocks the same?
People use the names interchangeably. Modern blocks are concrete masonry units (CMU) made with sand and gravel aggregate; true cinder blocks, made with coal cinders, are rarely produced today.
Do I need a footing for a block wall?
Yes. Block walls need a continuous concrete footing below the frost line. Use the concrete calculator to size the footing pour.