Masonry & Block Calculator (Blocks, Bags & Sand)
Enter your wall dimensions and get the concrete block count, mortar bags, and sand you need for the job — with a waste allowance built in so you are not making a second supply run mid-build. The math updates as you type.
Masonry & Block Calculator
Enter wall length and height, and read the blocks, mortar bags, and sand below. A waste percentage is added automatically.
Standard 16×8 in block face ≈ 0.888 sq ft. Mortar figured at about 3 bags per 100 block; bedding/joint sand at roughly 0.045 tons per mortar bag. Estimates only — confirm quantities with your block supplier.
How much block do I need? The formula
Masonry math starts with the wall face area, then converts that area into block count using the face size of a standard 16×8 inch concrete block — about 0.888 square feet per block once you account for the mortar joint. Add a waste allowance for cuts, corners, and breakage, then round up.
| Step | Example: a 40×8 ft wall, 10% waste |
|---|---|
| Wall area | 40 × 8 = 320 sq ft |
| Block needed | 320 ÷ 0.888 = 360.4 block |
| With 10% waste | 360.4 × 1.10 = 397 block |
| Mortar bags | 397 ÷ 33.3 ≈ 12 bags |
| Sand | 12 × 0.045 = 0.54 tons |
Always round the final block count up to a whole block, and never order to the exact number — broken block, bad cuts around openings, and corner waste are unavoidable on every job.
Contractor Estimate Calculator (Excel & Google Sheets)
Turn quantities into a priced, itemized estimate — materials, labor, markup, and profit, auto-totaled. The estimate you hand the client after the calculator tells you the block count.
Mortar and sand, sanity-checked
A common field rule of thumb is about 3 bags of mortar mix per 100 block laid, and roughly one 50‑lb bag of mason sand for every couple mortar bags depending on joint size. Wider joints, taller walls, and colder weather (more tooling and pointing) all push actual usage higher, so treat this number as a starting order, not a final one.
Related calculators
Pouring footings or a slab under that wall? Run it through the concrete calculator first. Once quantities are set, price the whole job with a construction estimate template so materials, labor, and markup are all in one document.
Frequently asked questions
How many concrete blocks are in a wall?
Divide the wall area in square feet by the block face area (about 0.888 sq ft for a standard 16×8 in block), then add a waste allowance. A 320 sq ft wall needs roughly 397 block with 10% waste.
How many bags of mortar per 100 block?
About 3 bags of mortar mix per 100 block laid is a common field estimate. Joint width, block size, and mason technique all shift this figure, so confirm with your mortar supplier for large jobs.
How much sand do I need for mortar?
Roughly 0.045 tons of sand per mortar bag is a workable planning number for bedding and joint sand. Order a little extra — sand is cheap and running out mid-wall is not worth the delay.
Is this masonry calculator free?
Yes — free, no sign-up. Enter your wall length and height and read the block count, mortar bags, and sand. Numbers are estimates; confirm with your block supplier before ordering.
Materials + labor + markup with the margin math handled — works for any trade.