Concrete Block Calculator
Work out how many concrete blocks, mortar bags and cubic yards of grout you need for a CMU wall. Enter the wall size, subtract doors and windows, and add waste.
Results are estimates for standard 8 by 16 inch face blocks with three eighths inch mortar joints. Check quantities against your drawings and supplier before ordering.
How to Calculate Concrete Blocks
A standard concrete block has a face of 8 by 16 inches including the mortar joint, which covers 0.89 square feet. That means you need about 1.125 blocks for every square foot of wall, no matter if the block is 4, 6, 8 or 12 inches thick.
For a wall 40 feet long and 8 feet high with one 3 by 7 foot door, the net area is 320 minus 21, or 299 square feet. At 1.125 blocks per square foot that is about 337 blocks, or about 354 with 5% waste.
Mortar for block walls
One 80 lb bag of premixed mortar lays roughly 13 standard blocks, depending on joint size and the mason. Projects that mix masonry cement and sand on site use far fewer bags, so use this as a planning number only.
Grout for filled cells
Reinforced block walls have grout in the cells that hold rebar. A fully grouted 8 inch wall needs about 0.26 cubic yards of grout per 100 square feet. If only the reinforced cells are filled, enter the share of cells that will be grouted.
| Block thickness | Blocks per sq ft | Grout per 100 sq ft, fully grouted |
|---|---|---|
| 4 inch | 1.125 | Usually not grouted |
| 6 inch | 1.125 | About 0.17 cubic yards |
| 8 inch | 1.125 | About 0.26 cubic yards |
| 12 inch | 1.125 | About 0.43 cubic yards |
Tips for an accurate block count
- Subtract door and window openings, but add bond beam, lintel and corner blocks as separate items.
- Add 5% waste for straight walls and more for walls with many corners and openings.
- Check the structural drawings for grout spacing and rebar before pricing grout.
- Count pilasters and columns separately from the main wall area.
Concrete Block Calculator Questions
How many blocks are in a square foot of wall?
About 1.125 standard blocks with an 8 by 16 inch face, including the mortar joint.
How many concrete blocks are on a pallet?
It depends on the supplier and block size. Many suppliers stack about 90 standard 8 inch blocks per pallet, so confirm with your yard.
How much mortar do I need for 100 blocks?
Roughly 8 bags of 80 lb premixed mortar, depending on joint size and waste. Masonry cement and sand mixed on site needs fewer bags.
Does this calculator include rebar?
No. Use our rebar calculator for bar quantities, or send your plans for a full masonry takeoff.
Can you do the full masonry takeoff for my bid?
Yes. We take off block, brick, grout, rebar, lintels and accessories from your drawings and deliver an editable Excel estimate, usually within 24 to 48 hours.
Need a Full Masonry Estimate?
Send your plans and get block, brick, grout and rebar quantities by wall type in editable Excel, usually within 24 to 48 hours.
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