Loan Concrete Block Estimator
Block walls price out by the unit. Enter the wall dimensions, choose the block, and get the CMU count and mortar bags — the same arithmetic a block supplier does at the counter, waste allowance included.
Block dimensions are nominal: an "8 × 8 × 16" block actually measures 7⅝ × 7⅝ × 15⅝ in, and the ⅜-in mortar joint brings it to the nominal size the math assumes. Openings for doors and windows: subtract their area by shortening the wall length, or run the wall in sections.
How it works
A standard block face is 8 × 16 in nominal — 128 sq in, or 1.125 blocks per sq ft of wall. Half-high blocks (4 in tall) double the courses and the count to 2.25 per sq ft. The estimator multiplies wall area by the blocks-per-sq-ft rate, adds your waste allowance, and counts mortar at about 9 bags of 80-lb premix per 100 standard blocks (12 per 100 half-high — twice the bed joints; 11 per 100 for 12-in block, whose joints carry more mortar). Those yields are the long-standing industry planning figures for ⅜-in joints.
Formula & worked example
Formula: Blocks = wall area (sq ft) × blocks per sq ft — 1.125 for 8-in-high faces (standard and 12-in-wide block), 2.25 for half-high 4-in block — plus waste. Mortar bags = blocks × bags-per-100 ÷ 100 (9 standard, 12 half-high, 11 wide), the standard premix yields at ⅜-in joints.
Worked example: A 20 × 8 ft foundation wall in standard block: 160 × 1.125 = 180 blocks — 198 with 10% waste — and 18 bags of mortar. The same wall in half-high block needs 395 blocks and 48 bags, because it has twice as many bed joints.
When to use this
- Building a foundation, retaining stem wall or garage and ordering block by the pallet.
- Checking a block supplier's count before the truck is loaded.
- Pricing a CMU garden or shed wall where mortar bags matter as much as blocks.
- Comparing standard vs half-high block for a stepped or low wall.
How to use it, step by step
- Measure the wall length and finished height (courses × 8 in for standard block).
- Choose the block: standard 8×8×16 unless the design calls for half-high or 12-in.
- Keep waste at 10% for straight walls; drop to 5% for long uninterrupted runs.
- Add the result's blocks, then ask the yard about bond-beam and lintel units for openings.
- Order mortar bags with the block — one delivery, one fee.
What the inputs mean
| Input | What it is | Typical values |
|---|---|---|
| Wall length & height | Finished wall dimensions | Foundations 20–60 ft × 2–8 ft |
| Block size | Thickness × height × length (nominal) | 8×8×16 standard most common |
| Waste % | Breakage and cutting allowance | 10% typical |
Another worked example
A stepped garden wall, 30 × 10 ft of face, in half-high block for a finer scale: 300 sq ft × 2.25 per sq ft = 675 blocks, 743 with waste. Mortar jumps to 90 bags — half-high block doubles the bed joints, and the joints are where the mortar goes.
Frequently asked questions
How many blocks do I need for a 20 × 8 ft wall?
A standard 8 × 8 × 16 block covers 1.125 per sq ft, so 160 sq ft needs 180 blocks — 198 with a 10% breakage allowance — and about 18 bags of 80-lb mortar mix.
Why do half-high blocks need more mortar per block?
Half-high block doubles the number of courses, so it doubles the bed joints per square foot of wall. Count on roughly 12 bags per 100 blocks instead of 9 — the wall goes up in smaller pieces with more mortar between them.
How many blocks are on a pallet?
Typically 90–120 standard 8 × 8 × 16 blocks per pallet depending on the yard. The default wall here (198 blocks) is about two pallets — worth knowing when you arrange delivery, since a pallet of block weighs over 3,000 lb.
Does wall thickness change the count?
Not the face count: 8-in and 12-in thick blocks share the same 8 × 16 face, so the count per sq ft is identical. Thickness changes weight, strength, mortar per joint slightly, and cost per block — not how many faces cover the wall.
What waste percentage should I use?
Ten percent is the standard planning figure for straight walls. Long walls with few cuts can run 5%; walls with many openings, corners and gable ends justify 12–15%.
🧱 Pricing brick instead?
Same wall, different unit: the Brick Estimator counts bricks and mortar bags by brick size and joint thickness.
How many concrete blocks per pallet should I expect to pay for?
Yards sell by the unit but deliver by the pallet (roughly 90–120 standard blocks). Ask whether partial pallets carry a restocking or breakage fee — ordering to the pallet boundary (as the counts here let you plan) avoids it.
Do I need grout and rebar in the count?
For structural or retaining walls, yes — vertical rebar and grout-filled cells are structural requirements in most codes, figured separately from the block and mortar here. A non-structural garden wall under local height limits often needs neither; check your jurisdiction.