Count concrete blocks for a wall — area, exact count, waste-inclusive order and mortar bags.
Standard concrete blocks are laid with mortar joints, so the calculator uses the nominal face size (including the joint). Add openings later by subtracting their area — or enter the net wall area as length × height.
Blocks to order
How to use this tool
Length and height in feet or metres — the net wall area.
Standard 8×8×16 in CMU is the default; half and larger blocks are offered.
10% covers cuts, breakages and uneven courses.
Blocks with waste, plus an approximate mortar count.
Formula & worked example
A 10 ft × 8 ft wall is 80 ft². At 1.125 blocks per ft² that is exactly 90 blocks, or 99 blocks with 10% waste, plus about 1 bag of mortar (use more for grouted or reinforced walls).
Limitations — read this before you rely on it
Counts assume a single-wythe wall with no openings. Subtract door and window areas from the wall area first, or the count will be high. Mortar use varies with joint size, block absorption and whether cores are grouted — confirm with your supplier. This is an estimate, not a structural design.
Frequently asked questions
Divide the wall area by the block face area: standard 8×8×16 in blocks need 1.125 blocks per square foot, so an 80 ft² wall needs 90 blocks before waste.
Nominally 8×8×16 inches; the actual block is slightly smaller (about 7⅝ × 7⅝ × 15⅝ in) so mortar joints bring each course to the nominal size.
10% is standard for straight walls; allow 15% for walls with many cuts, corners or openings.
Roughly one 80 lb bag per 100 ft² of standard block wall, but joint size and grouting change this — buy a little extra.
Yes. Work out the net wall area (total minus openings) first, then enter that as length × height, or the count will over-order.