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Concrete Block Calculator
Enter a wall to get blocks, courses, mortar, grout, vertical bars and joint reinforcement for 4 to 12 inch CMU. Add your own prices to get the installed cost, then add the wall to an estimate and do the next one.
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Wall
Grout and reinforcement
Bar size, spacing, grouted cells and joint reinforcement come from the plans, the engineer and the local code (TMS 402, IBC). Enter what the drawings show.
Mortar and grout supply
Leave the mortar rate blank to use the typical rate for the block width. Your mason’s own count is better than any table.
Your prices
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Your estimate
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Start free trialHow it’s calculated
Wall area and blocks. Wall area is length × height, less the openings you deduct. A standard block has an 8 × 16 inch nominal face, which covers 8/9 sq ft, so blocks laid = area × 1.125, rounded up (CMHA TEK 04-02A). Your waste percentage goes on top of that for the order. Courses are the height in inches ÷ 8.
Mortar. Bags = blocks laid ÷ blocks per bag, rounded up. Waste on broken block is left out, because broken block takes no mortar. The typical rate per 80 lb bag of preblended mortar is the middle of the ranges SPEC MIX publishes, typical waste included: 16 for 4 in block, 13 for 6 in, 12 for 8 and 10 in, and 11 for 12 in. A 60 lb bag lays ¾ as many and a 3,000 lb bulk bag 37½ times as many. Wet mortar is 0.7 cu ft per 80 lb bag. Rates vary with the bedding, the joints and the crew, so enter your own when you have it.
Grout. A fully grouted wall takes area × the CMHA TEK 04-02A Table 3 volume for two-core units with 3% waste: 25.6, 36.1, 47.0 and 58.9 cu ft per 100 sq ft for 6, 8, 10 and 12 in block. Grouting only the bar cells takes bars × courses cells, each 1/225 of the fully grouted volume per 100 sq ft, because cells sit 8 in apart in 8 in courses. Cubic yards are cu ft ÷ 27, and ready-mix grout goes on the estimate rounded up to the quarter yard. Bagged grout is figured at 0.65 cu ft per 80 lb bag (Quikrete Core-Fill Grout). CMHA does not recommend grouting 4 in block, so the calculator does not grout it. Bond beams and lintels take more grout and are not included.
Vertical bars. Bars = wall length in inches ÷ spacing, rounded up, plus one, so there is a bar at each end. Each bar runs the wall height, and sticks hold as many whole bars as fit. Lap splices to footing dowels and between sticks, and extra bars at openings, corners and wall ends, come from the plans and are not counted.
Joint reinforcement. Rows = (courses − 1) ÷ the course interval, rounded up, starting in the first bed joint above the bottom course. Linear feet = rows × wall length. Laps and prefabricated corners and tees are extra.
Price. Material is quantity × your unit price for each item you priced, with grout priced by the yard or by the bag as you buy it. Labor is blocks laid × your rate per block. Nothing is priced with numbers you did not enter.
Reinforcement, grout spacing, bond beams and lap lengths are design decisions. They come from the plans, the engineer and the local code under TMS 402 and the IBC, and this calculator does not check them. Pricing the slab or flatwork next to the wall? The concrete estimate template has a slab takeoff for cubic yards, rebar and forms.
Material prices. The concrete price trend covers block, cement and ready-mix, and steel and rebar prices cover the bars.
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Frequently asked questions
How many concrete blocks are in a square foot of wall?
A standard block has an 8 × 16 inch nominal face, which covers 8/9 of a square foot, so a wall takes 1.125 blocks per square foot, or 112.5 per 100 sq ft. CMHA TEK 04-02A rounds that to 119 per 100 sq ft with a 5% allowance for waste and breakage. The count is the same for 4, 6, 8, 10 and 12 inch block, because the face size does not change with the width.
How many blocks do I need for a 10 × 8 wall?
A wall 10 ft long and 8 ft high is 80 sq ft, so it takes 90 blocks: 12 courses of 7½ blocks. With 5% waste, order 95. Deduct doors and windows from the wall area first, and count corner, bond beam and lintel units separately where the plans call for them.
How many courses of block are in an 8-foot wall?
Twelve. A course is 8 inches nominal, a 7⅝-inch block plus a ⅜-inch mortar joint, so 96 inches ÷ 8 = 12 courses. A height that is not a multiple of 8 inches leaves a partial course, cut or laid with half-high units. With joint reinforcement every other course, an 8-foot wall gets 6 rows, starting in the first bed joint above the bottom course.
How much mortar do I need for 100 blocks?
About 8⅓ bags of 80 lb preblended mortar for 100 8-inch blocks, so buy 9. SPEC MIX rates its 80 lb bag at 11 to 13 8-inch blocks, typical waste included, and at about 0.7 cu ft of wet mortar, which works out to about 5.8 cu ft per 100 blocks. Quikrete and Sakrete put their 80 lb bags at up to 13 and 12 blocks. CMHA TEK 04-02A, which assumes mortar on the face shells only, uses 16. Your mason’s own count is the best rate, so the calculator lets you enter it.
How much grout does a fully grouted 8-inch block wall take?
CMHA TEK 04-02A puts it at 36.1 cu ft per 100 sq ft of wall, 3% waste included, which is about 1.34 cu yd per 100 sq ft. A 10 × 8 wall fully grouted takes 28.9 cu ft: 1.07 cu yd, or about 45 bags of 80 lb core-fill grout at 0.65 cu ft a bag. The same table gives 25.6 cu ft for 6-inch, 47.0 for 10-inch and 58.9 for 12-inch block.
How much grout if only the cells with rebar are grouted?
In 8-inch block, each grouted cell takes about 0.16 cu ft per course: the fully grouted volume spread over 225 cells per 100 sq ft. A 40 × 8 ft wall with bars at 48 inches on center has 11 bars, one at each end and one every 4 ft between, so 132 grouted cells over 12 courses: 21.2 cu ft, or about 0.78 cu yd. Bar size, spacing and which cells get grout come from the plans, the engineer and the local code under TMS 402 and the IBC. The calculator counts what you enter; it does not design the wall.
Are my measurements and prices sent to BuildWorkPro?
The calculator sends nothing: the math runs in your browser, and your prices and your estimate are saved in this browser’s local storage, never on our servers. The wall size is kept in the page address so you can bookmark or share a result; like any page address, it is recorded by our site analytics if you accept analytics cookies.