A block wall calculator counts the concrete masonry units a wall needs from its area, because a standard block with its mortar joint covers a known face: an 8 by 16 inch block laid with a 3/8-inch joint covers 8 by 16 inches of wall, 128 square inches, so a square foot of wall takes 1.125 blocks. From the block count follow the mortar, the grout for the cells that are filled, the rebar in them, and the footing under the wall, which is a concrete sum. This page works a 40-foot wall 8 feet high, says what the corners, openings and bond beams add, and works the footing with the free concrete calculator on this site, which does that arithmetic from your own dimensions, with no account.
Blocks from the wall's area
Blocks equals wall area in square feet times 1.125 for standard 8 by 16 face blocks, plus the contractor's waste allowance for cuts and breakage. A 40-foot wall 8 feet high is 320 square feet, 360 blocks, and at a 5% allowance 378. In courses: 8 feet of height at 8 inches a course is 12 courses, and 40 feet of length at 16 inches a block is 30 blocks a course, 12 times 30 is 360, the same answer by the other route and a useful check. Openings are deducted by their area, a 3 by 7 door being 21 square feet or about 24 blocks, and the cuts at their jambs are part of the waste allowance. The American Concrete Institute publishes the masonry specifications the units and the joints are laid to.
Mortar, grout and rebar
Mortar is counted per block at the coverage the mix states: a bag of masonry mortar lays a stated number of standard blocks at a 3/8-inch joint, so 378 blocks divided by the blocks per bag is the bag count, rounded up with the contractor's allowance for droppings. Grout fills the cells that carry rebar, and for a wall with every cell filled the grout volume is the wall's length times height times the cell area per foot the block's maker states, in cubic feet, divided by 27 into yards; for a wall with bars at 32 inches on center the filled cells are a quarter of them. Rebar is the bar count times the wall height plus the laps. The Portland Cement Association publishes the mortar and grout specifications the mixes are made to.
Bond beams, corners and the top course
A bond beam course replaces a course of standard block with a channel block that is filled and reinforced across the wall's length, commonly at the top and at the lintel line over openings, so the count includes those courses in bond-beam units rather than standard units, and their grout runs the full length. Corners use corner blocks or a half block to keep the bond; a wall with two corners adds a handful of specials per course. A cap course, if one is laid, is its own count at its own unit. The block wall calculator's total is therefore standard units, specials by type, mortar bags, grout yards and rebar feet, which is the order the yard prices.
The footing under the wall, worked as concrete
The footing is a long slab: for the 40-foot wall, a footing 2 feet wide and 1 foot deep is 40 by 2 by 1, 80 cubic feet, 2.96 yards, 3.3 yards with a 10% allowance, ordered as 3.5. The free concrete calculator on this site works that from the footing's dimensions and the supplier's price per yard, and the wall's lines, block, mortar, grout, rebar, footing and the contractor's own labor rate to lay the wall, go into the estimate marked up at the contractor's overhead and profit. The schedule of values then carries the wall as one value for the draw, which is why one count, done once, matters.
Questions people ask about block wall calculator
How many blocks are in a 40 by 8 wall?
320 square feet times 1.125 is 360 standard 8 by 16 blocks, 378 with a 5% waste allowance; or 12 courses of 30 blocks, the same by the other route. Deduct openings by area.
How much mortar does a block wall need?
The block count divided by the blocks a bag of masonry mortar lays at a 3/8-inch joint, as the mix states, rounded up with the contractor's allowance for droppings.
How is the footing calculated?
As concrete: length times width times depth in feet, divided by 27. A 40-foot footing 2 feet wide and 1 foot deep is 2.96 yards, ordered as 3.5 with waste.