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Calculation report
A focused summary of the selected takeoff, active materials and costs. Changes are saved automatically in this browser.
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Wall-by-wall quantities
| Wall | Gross area | Openings | Net area | Blocks / course* | Courses* | Net block equivalents |
|---|
*Course figures are gross module layout guides, before openings. Partial courses/cuts and bond patterns are not optimized. The order calculation uses unrounded net area.
Purchase list & priced costs
| Item | Purchase quantity | Entered rate | Line cost |
|---|
Wall elevation
Add positions to openings if you want them shown.
Compare takeoff options
Compare up to three scenarios while changing waste, block sizes or supplier prices.
Worked example: 20 × 6 ft CMU wall
With no openings, the wall is 120 ft². A 16 × 8 in module covers 128 ÷ 144 = 0.888889 ft², so 120 ÷ 0.888889 = 135 full-block equivalents. Applying 5% once gives 141.75 → 142 blocks. There are 15 gross full modules per course and 9 courses.
The selected product example covers up to 13 standard blocks per 80 lb mortar bag. On installed equivalents, 135 ÷ 13 × 1.10 = 11.423 → 12 bags with the entered 10% extra allowance. That allowance is a scenario choice, not a product requirement. Grout and reinforcement are off until specified.
A 3 × 7 ft door would reduce net area to 99 ft²: 111.375 theoretical equivalents and 117 ordered at 5%. This is still an area estimate, not a cut-by-cut masonry bond plan.
Inputs explained — what changes the answer?
- Actual dimensions plus the joint: entering nominal dimensions and adding another joint double-counts the joint and underestimates block count.
- Openings: quantities multiply width × height. Positioned single openings are checked for overlap; unpositioned groups need your review.
- Thickness: a wider block with the same face module does not change wall coverage, but its bedding, core volume and weight can change.
- Waste and pallets: these affect purchases. Mortar/grout use installed area equivalents, not spare stock.
- Reinforcement: enter the specified schedule. More detailed bars at openings/corners belong in manual totals, not an invented default.
Module reference & preset provenance
| Nominal face / selected module | Area per unit (ft²) | Units per 100 ft² |
|---|---|---|
| 16 × 8 in | 0.888889 | 112.5 |
| 16 × 4 in | 0.444444 | 225 |
| 8 × 8 in | 0.444444 | 225 |
Counts exclude waste and openings. The current custom-module row updates from the engine. Standard actual-dimension convention: CMHA; verify tolerances and shapes with your manufacturer.
- CMU presets: nominal 4/6/8/10/12 × 8 × 16 in; actual dimensions nominal minus ⅜ in. The joint is an independent editable input.
- Mortar example: QUIKRETE 1102, 80 lb bag, up to 13 standard 8 × 8 × 16 units. No generic mixed-volume yield is assigned.
- Grout yield example: QUIKRETE Fine Core-Fill #1585-08, 0.68 ft³ per 80 lb bag. The block’s cell volume must still be supplied.
- Rebar weight presets: Harris/Nucor supplier table, #3–#8; custom mass per length supported. This does not select reinforcement.
- Waste, pallet count, wall dimensions, costs and shell-bedding depth are editable scenario inputs, not universal recommendations.
Formula & methodology
Net wall area = Σ(length × height) − Σ(opening quantity × width × height)
Theoretical blocks = net wall area ÷ module face
Order target = ceiling(theoretical blocks × (1 + block waste / 100))
Common blocks = ceiling(order target − specialty replacement equivalents)
Coverage mortar bags = ceiling(installed equivalents ÷ bag coverage × allowance)
Joint mortar volume = installed equivalents × (module face − actual face) × effective bedding depth
Grout = (cell equivalents × net void per cell × fill-height fraction + extra void) × allowance
Rebar stock minimum = ceiling(allowed aggregate length ÷ stock length) + manual extra bars
Rounding is applied at purchasing steps, not repeatedly to each opening or wall’s area-based quantity. Geometry mortar is an idealized joint model; enter additional bedding volume before its allowance. Specialties use final purchase counts. Costs use purchase-rounded bags/bars and the standard-block pallet option you selected.
Common mistakes to avoid
- Adding a joint to nominal block dimensions instead of actual dimensions.
- Subtracting the same opening twice, or overlapping unpositioned openings.
- Filling waste/spare blocks or counting bond-beam grout twice.
- Using a generic concrete bag yield for mortar or the specified masonry grout.
- Adding specialty blocks without saying which common units they replace.
- Treating an aggregate rebar length as a cutting plan or structural schedule.
Assumptions, limitations & sources
For estimating mortared CMU quantities. Not structural design or a guarantee of delivery quantities. Check actual product dimensions, core voids, packaging, materials and the project schedule. Footings, drainage, formwork, excavation, bracing and reinforcement details are excluded unless separately entered as manual costs/quantities. No organization below endorses Efficienco.
- CMHA: concrete masonry unit shapes, sizes and properties — nominal versus actual dimensions.
- QUIKRETE Mortar Mix 1102 data sheet — product-specific coverage.
- QUIKRETE Fine Core-Fill Grout manufacturer data sheet (BuildSite copy) — example mixed yield, not a universal core volume.
- Harris Supply Solutions / Nucor: rebar sizes and weights — mass per length.
Method/data reviewed September 2, 2026 · Engine cmu-1.0.0 · Prices are entered by the user.