PreConstruct AIFree calculator
Concrete block calculator — blocks, mortar and grout
Pick the block face, type the wall length and height and take off the openings. Get the blocks, the mortar bags and, where cores are grouted, the grout — with every rate yours to change.
Block face
Blocks
709
8 × 8 × 16 nominal
Wall area
600 SF
55.74 m²
Mortar
21 bags
Grout
—
set cores grouted
The working
- wall 80 ft × 8 ft − openings 40 SF = 600 SF
- 600 SF × 1.125 a SF = 675 blocks laid
- × waste of 5 per cent = 709 blocks
- mortar 675 ÷ 100 × 3 bags = 21 bags
A starting figure, not an engineered quantity. Sizes, reinforcing and code requirements come from your drawings, your specifications and your engineer — check them before you order.
Where a calculator stops
This does one run, from numbers you type. A bid is every run on every sheet.
- — It doesn't read the drawing set or its schedules
- — It doesn't measure on the PDF or keep the lengths
- — It doesn't show what an addendum changed
- — It doesn't price, add labour or build a proposal
Blocks
An 8 × 16 in nominal block — 7⅝ × 15⅝ in plus a ⅜ in joint — covers 0.889 SF, so a wall takes 1.125 blocks per SF. The Canadian metric unit, 190 × 390 mm plus a 10 mm joint, covers 0.08 m², or 12.5 blocks per m². Add waste for cuts and breakage.
Mortar
A common starting figure is about three bags of masonry cement, with sand, per 100 blocks at ⅜ in joints. Pre-mixed mortar bags yield far less mortar each, and thicker joints take more — set the rate from the bag you buy.
Grout
Only the cores the drawings call to be grouted: reinforced cells, bond beams, or the whole wall. About one cubic yard fills 100 standard 8 in blocks solid — 0.27 ft³ a block — but core volume varies by block maker, so use theirs.
What this does not decide
Block width, reinforcing, which cells are grouted and the mortar type come from the structural drawings. This counts and measures from what they show.
Questions estimators ask
- How many concrete blocks per square foot?
- 1.125 for a standard 8 × 16 in nominal block. For Canadian 20 cm metric block (190 × 390 mm) it is 12.5 per square metre.
- How much mortar for 100 blocks?
- A common starting point is about three bags of masonry cement mixed with sand at 3/8 in joints. Premixed bags make less each. Check the bag's yield.
- How much grout to fill 8 inch block?
- Roughly one cubic yard fills 100 standard 8 in blocks solid, about 0.27 cubic feet a block. Core sizes vary by manufacturer, and usually only some cells are grouted — the drawings say which.
- What is a 20 cm block in inches?
- A metric 20 cm unit is 190 × 190 × 390 mm, about 7½ × 7½ × 15⅜ in — close to, but not the same as, an imperial 8 × 8 × 16.
Stop retyping sizes into a calculator
On PreConstruct AI you measure on the PDF, type the sizes the drawings print, and the concrete, forms, bars, board and stringers come out with the arithmetic beside every line — in imperial, metric or both. Your first bid is free, with no card.