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BuildQuantify
Estimate how many concrete blocks and mortar bags a wall needs.
Estimate only, based on 1.125 standard blocks per sq ft, ~3 bags of Type S mortar per 100 blocks (3/8" joints), and ~0.15 cu ft of grout per fully-filled core (80 lb bag ≈ 0.6 cu ft yield). Actual coverage varies by block manufacturer, joint thickness, and rebar/grout spec — confirm with your supplier or engineer for structural or large orders.
| Wall | Date | Dimensions | Net Area | Blocks | Mortar Bags | Grout Bags | |
|---|---|---|---|---|---|---|---|
| No entries yet — calculate above and click "Save". | |||||||
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Standard CMU blocks have a nominal face of 16" × 8", which works out to 1.125 blocks per square foot of wall — a widely used estimating shortcut in masonry. Net wall area (gross area minus door/window openings) multiplied by that ratio, then bumped up for waste, gives the block count.
Mortar coverage depends on joint thickness and block size, but a common rule of thumb for standard 3/8" joints is about 3 bags of Type S mortar mix per 100 blocks. This calculator uses that ratio — for a precise order on a large job, your block supplier can typically give a more exact figure based on their specific product.
For reinforced walls, vertical rebar is typically "set" in place by filling specific cores with grout. A standard 8" CMU core holds roughly 0.15 cubic feet of grout when fully filled. Entering the percentage of cores being grouted estimates the grout bag count (based on an 80 lb bag yielding about 0.6 cubic feet) — but core spacing and rebar schedules are structural decisions your engineer or local code should specify, not something this calculator determines for you.
Say you need to price a single-wythe wall that is 40 ft long and 8 ft high, with one 3 ft × 7 ft door opening and one 4 ft × 3 ft window opening. Here is how the numbers work out, so you can check the calculator against your own hand figures.
| Step | Calculation | Result |
|---|---|---|
| Gross wall area | 40 × 8 | 320 sq ft |
| Openings | (3 × 7) + (4 × 3) | 33 sq ft |
| Net wall area | 320 − 33 | 287 sq ft |
| Blocks before waste | 287 × 1.125 | 323 blocks |
| Blocks with 5% waste | 323 × 1.05 | 340 blocks |
| Mortar (3 bags per 100) | 340 ÷ 100 × 3 | about 10.2, so order 11 bags |
Grout depends on how many cores are filled. If your structural drawings call for grouted cores at a given spacing, enter that as a percentage of cores and the calculator converts it to bags. Always confirm the spacing and bar sizes with the structural drawings.
How many blocks are in a pallet?
It varies by block size and supplier, so ask your supplier. Standard 8-inch blocks are commonly delivered on pallets of around 90 blocks, but do not rely on that figure for an order.
Does this calculator include half blocks, corner blocks and lintels?
No. It estimates the total number of standard blocks from the net wall area. Specialty units such as bond beam blocks, lintel blocks and corner returns should be counted from the drawings.
Is the mortar estimate exact?
No, it is a rule of thumb for 3/8 in joints. Mason skill, block texture and waste all change actual use, so treat it as a budgeting number and check with your supplier for large orders.
Can I use this for brick?
No. Brick uses a different unit size and mortar quantity, so use a brick-specific method.
Last updated: September 21, 2026