Enter your wall's length and height to get block count, mortar bags needed, and estimated cost.
The Block Calculator helps you figure out exactly how much material to buy before you order a truck or make a hardware store run. Enter your wall's length and height to get block count, mortar bags needed, and estimated cost. Instead of guessing at cubic yards or bag counts and hoping it's close, you enter the numbers you already have — the measurements from your plan, tape measure, or job site — and get a precise, ready-to-order figure back in seconds.
This tool is built for two kinds of people: contractors running a fast takeoff between jobs who need a number they can call into a supplier immediately, and homeowners or first-time DIYers who don't want to either overspend on wasted material or come up short mid-pour. Every calculator on ConcreteYard uses the same standard, industry-typical assumptions — 150 lb per cubic foot for normal-weight concrete, standard bag yields, and common mix ratios — so the numbers here should line up closely with what your supplier or hardware store confirms when you place the order.
Whether you're pricing out a job, planning a delivery, or just want to know how much to buy at the store today, this calculator gives you a number you can act on immediately — no spreadsheet, no account, and no guesswork required.
Standard CMU (concrete masonry unit) face is 8in high × 16in long.
1. Measure accurately. Get exact dimensions in the units the calculator asks for — feet for length and width, inches for thickness are the most common setup. A rough guess in, a rough number out; precise measurements are what make this tool worth using over a mental estimate.
2. Enter your numbers. Fill in the fields above with your project's actual measurements. Default values are pre-filled as a sane starting point — replace every one of them with your real numbers before you rely on the result.
3. Adjust the settings. Where available, set your waste percentage, bag size, or price per yard to match your job. These small adjustments are what separate a rough ballpark from an order-ready figure.
4. Read the batch ticket. Click calculate and use the highlighted total as your order quantity — it already accounts for waste and rounds to a practical ordering increment where relevant.
Block count = wall area ÷ block face area. A standard 8×16in block has a 0.888 sq ft face, so a 20×6 ft wall (120 sq ft) needs about 136 blocks before waste.
Corners, openings (doors, windows), and cut blocks all add breakage — the 10% default waste factor covers typical jobsite loss.
This estimator counts block units, not fill volume. If you're grout-filling hollow-core block cores (common for reinforced CMU walls), use the Cylinder & Post Calculator per-core, or ask your supplier for a fill-volume table for your block type.
Divide the wall's square footage by the block's face area. For standard 8x16in block (0.888 sq ft face), that's roughly 1.13 blocks per square foot — this calculator does that math from your wall's length and height.
Roughly 3 bags of Type S mortar mix per 100 standard concrete blocks, assuming standard 3/8in joints. Thicker joints or oversized block will use more.
The most common CMU (concrete masonry unit) has an 8 x 8 x 16 in nominal size, with an actual face of about 7.625 x 15.625 in to allow for mortar joints.
Skipping the waste factor. Uneven subgrade, formwork gaps, and simple spillage routinely eat 5–10% of your raw calculated volume. Ordering the exact math-perfect number is one of the most common ways to come up short mid-pour.
Rounding down instead of up. Ready-mix trucks deliver in fractions of a yard, but suppliers set order minimums. If your number lands at 4.1 yards, round to 4.25 or 4.5, not down to 4.
Mixing up units. Thickness is almost always in inches while length and width are in feet — plugging inches into a feet field (or vice versa) is the single most common calculator input error.
Treating irregular shapes as one rectangle. An L-shaped or curved area isn't one simple calculation. Break it into rectangles, run each section separately, and add the totals together for an accurate figure.
Order slightly more than the bare minimum — a short-load fee for a second truck almost always costs more than the extra material would have. Confirm your supplier's order minimum and short-load fee before you finalize a quantity that's close to the cutoff.
Check the weather. Concrete needs temperatures generally above 40°F to cure properly without special cold-weather additives, and pouring in direct heat or high wind can cause the surface to dry and crack before it has a chance to properly set.
Have everything staged before the truck arrives — forms set, base compacted, tools (screed board, bull float, edger) on site, and enough hands to place and finish the pour before it starts to set.
Plan your control joints in advance for any flatwork. Joints control where concrete cracks as it cures and shrinks — skipping them doesn't prevent cracking, it just makes the cracks unpredictable.
Yes — it uses standard, industry-typical formulas and material assumptions (150 lb/cu ft concrete, standard bag yields, common mix ratios). For structural or permitted work, always confirm final quantities with your supplier or engineer.
No. Every calculator on ConcreteYard runs entirely in your browser, works instantly, and requires no sign-up, login, or download.
Yes — every tool on this site is built to work the same on a phone as it does on a desktop, so you can run the numbers standing at the job site before you call in an order.
Every tool below shares the same 150 lb/cu ft mix assumption, so figures stay consistent across your takeoff.