Concrete Block Calculator
Enter your measurements
Extra to cover cuts, breakage, and mistakes.
Results
- Blocks needed189 blocks
- Wall area160 sq ft
- Mortar (80 lb bags)6
Estimated cost
per standard 8×8×16 block (material)
Material cost is the block only at retail; mortar, rebar, and grout fill are extra. Installed cost per block reflects mason labor plus materials for a straightforward wall — corners, bond beams, or engineered designs push toward the high end.
Estimate only — prices vary by region, supplier, and season. Get a local quote before buying.
This concrete block calculator tells you how many standard CMU blocks and bags of mortar a wall needs before you place a single order. Enter your wall length and height, pick a waste allowance, and you get a block count, total wall face area, and an 80 lb mortar bag estimate in seconds. That saves headaches because concrete masonry units are sold individually at home centers or by the cube at masonry yards, and counting hundreds of blocks by hand invites costly rounding errors. The calculator assumes the standard 8x8x16 inch CMU, whose nominal face covers 16 inches wide by 8 inches tall, or 1.125 square feet per block. A 5% waste factor is sensible for a simple straight wall; raise it to 7-10% if your layout has corners, bond beams, control joints, or many cut blocks. Mortar is estimated at roughly one 80 lb bag of pre-blended type N or type S mix per 33 blocks, which covers both the bed and head joints at a standard 3/8-inch thickness.
How it’s calculated
Blocks = Wall area × 1.125 (a standard 8×8×16 block covers 16″×8″ of wall), plus waste. Mortar ≈ 1 bag per 33 blocks.
Worked example
For a 30-foot-long wall standing 8 feet tall with a 5% waste allowance, the calculator returns 284 blocks across 240 square feet of wall face. At one 80 lb mortar bag per 33 blocks, that wall needs 9 bags of mix — a quantity homeowners routinely underestimate when loading the cart.
Inputs
- Wall length
- 30 ft
- Wall height
- 8 ft
- Waste / overage
- 5 %
Result
- Blocks needed
- 284 blocks
- Wall area
- 240 sq ft
- Mortar (80 lb bags)
- 9
- Estimated material cost
- $426 – $852
Materials & pricing near you
Basic gray 8x8x16 CMU runs roughly $1.50 to $3.00 per block at big-box stores, while split-face, colored, or lightweight units cost more. Masonry yards sell by the cube — commonly around 90 blocks — and quote lower per-unit pricing on full-cube orders, so contractor and DIY retail prices can diverge sharply. Demand and prices tend to climb through spring and early summer as the building season peaks. Delivery is usually available but carries a minimum order, often a full cube, plus a flat truck fee that can add $75 to $200 by distance; rural markets see thinner supply and higher freight. Many jurisdictions require a permit for freestanding walls taller than about 4 feet, so confirm local codes before you break ground.
Frequently asked questions
What block size does this calculator assume?
It uses the standard 8x8x16 inch CMU, with a nominal face 16 inches wide and 8 inches tall that covers 1.125 square feet. This is by far the most common block in US residential and light commercial work. For 4-inch or 6-inch units, or a half-height block, adjust your inputs because the face area per block — and therefore the block count — will differ.
How do I handle a wall with doors or windows?
Calculate the full solid wall area first, then subtract each opening. A 3-foot-wide by 7-foot-tall door removes 21 square feet, and a 3-by-4-foot window removes 12 square feet, so deduct those from the total before reading the block count. Subtracting openings also keeps the mortar estimate honest, since fewer blocks means fewer bed and head joints to fill.
Why is mortar estimated in 80 lb bags?
The 80 lb bag is the standard pre-blended type N or type S masonry mortar sold at US home centers and masonry yards. One bag yields enough mortar for roughly 33 standard CMU at a 3/8-inch joint. If you buy 60 lb bags instead, divide your block count by about 25 to get the bag count, since each bag holds proportionally less mix.
When should I hire a mason instead of laying block myself?
Load-bearing walls — anything carrying a floor, a roof, or lateral pressure from retained soil — should be laid by a licensed mason in most jurisdictions. A short freestanding garden wall under 3 feet is manageable for a careful DIYer. Once the design calls for vertical rebar, grouted cells, bond beams, or engineering for seismic or wind loads, professional installation is the right call.