Sourced construction math
Construction calculators that show their math.
Every number here is traceable to a named source, and we show it right next to the result. So the contractor pricing a job and the engineer checking the takeoff see the same evidence.
- 20×
- Spread in per-block grout figures published elsewhere
- 0.32 ft³
- Our sourced volume for one 8 in block, from CMHA TEK 09-04A
- 100%
- Of constants cited to a named ASTM, CMHA, or datasheet source
Why trust these numbers
Most calculators hide the constants. We put the source in your hands.
When you cannot see where a number came from, you cannot check it, and a bad constant quietly becomes a bad material order. We do the opposite.
Every constant is cited
Behind each result is a sourced value: the figure, its unit, and the standard it comes from, shown inline so you can check it.
Two methods, never blended
Where an industry table and a geometric derivation disagree, we report both and name each, instead of averaging them into a number nobody can trace.
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Concrete Block Fill Calculator
Grout volume, cubic yards, and bag count for filling CMU walls, each with the source shown next to the number.
Order this much grout · CMHA method
2.14 yd³
57.76 ft³ · 97 × 80 lb bags
C90 minimum-thickness geometry
2.12 yd³57.17 ft³
Bare cell volume at ASTM C90 minimum face shell and web, plus your waste %. Carries no CMHA field allowance.
These two numbers land close together, and that is the point. The geometric figure uses ASTM C90 minimum face shell (1.25 in) and web (0.75 in) thicknesses, which produce the largest cell volume the standard allows: 0.303 ft³ per 8 in block. CMHA Table 2 reports 0.321 ft³ per block once field waste and overfill are included. Real units are usually made thicker than C90 minimums, so a wall built from typical block needs less than either figure. Order to the CMHA number. Why the two numbers differ.
Bond beam grout: 0.00 ft³ (0.00 yd³)
Added on top of both figures. CMHA Table 2 excludes bond beams and other horizontal grouted courses, so this is computed separately.
Inputs used
- Block count
- 180
- Wall area
- 160 ft²
- Blocks / ft²
- 1.125
Structural safety notice
This tool provides estimates for planning only and is not a substitute for a licensed structural or civil engineer. Do not use these results for load-bearing, safety-critical, or code-compliance decisions.
Guides
Know before you order
How Much Concrete to Fill Cinder Blocks
The real per-block volume, and why published figures scatter 20-fold.
Read guide →Should You Fill Cinder Blocks With Concrete?
When filling earns its cost, when it is wasted, and what to fill with.
Read guide →Partial Grouting: Why Spacing Changes Your Order by 5.9x
Solid vs partial fill, read from the CMHA grout table.
Read guide →Categories
What we cover
Masonry is live now. Concrete, aggregates, and structural estimators follow, each built on the same sourced-data foundation.
Masonry
LiveBlock fill, block counts, mortar, and CMU reference data.
View tools →Concrete
SoonSlabs, footings, columns, and ready-mix ordering.
Aggregates
SoonGravel, sand, and base course by volume and weight.
Structural
SoonRebar, bearing, and load-related estimators.