Concrete Block Calculator

Calculate concrete blocks for one or more walls, subtract openings, add an editable waste allowance, and estimate pallets and material cost. Enter the nominal block face module including the mortar joint.

How to use the concrete block calculator

Choose US customary or metric units.
Enter one wall’s length and height and the number of identical walls.
Subtract the combined face area of doors and windows.
Enter the block’s nominal face module including its joint. A supplier may describe the physical block and its nominal module differently.
Set an allowance based on cuts, breakage and your project’s ordering policy. Enter the actual pallet count and price from your supplier.

Concrete block calculation formula

Gross wall area = wall length × wall height × number of walls

Net wall area = gross wall area − openings

Blocks before waste = ceiling(net wall area ÷ nominal block face area)

Blocks to order = ceiling(blocks before waste × (1 + waste % ÷ 100))

The calculator rounds upward because partial blocks cannot normally be ordered as whole units. Pallets are also rounded upward. If a supplier sells partial pallets, use the block total rather than the pallet result.

Worked examples

1. A 20 ft by 8 ft wall

With no openings and a 16 in × 8 in nominal module, the wall has 160 ft² and each module covers 0.8889 ft². The result is 180 blocks before waste and 189 blocks with 5% extra.

2. Wall with a door and window

A 30 ft × 10 ft wall has 300 ft². Subtracting 33 ft² of openings leaves 267 ft². A 16 in × 8 in module requires 301 blocks before allowance and 323 blocks with 7% extra.

3. Metric wall

A 10 m × 2.4 m wall minus 3.6 m² of openings leaves 20.4 m². A 400 mm × 200 mm nominal module covers 0.08 m², so the result is 255 blocks before allowance and 268 blocks with 5% extra.

4. Long garden wall

A 40 ft × 6 ft wall minus 32 ft² of openings leaves 208 ft². A 16 in × 8 in module requires 234 blocks before allowance and 258 blocks with 10% extra.

5. Two identical walls

Two 12 ft × 8 ft walls total 192 ft². Subtracting 20 ft² leaves 172 ft². With a 12 in × 8 in nominal module, the result is 258 blocks before allowance and 271 blocks with 5% extra.

6. Pallets and cost

If the calculated order is 525 blocks, a pallet quantity of 90 gives 6 whole pallets. At 2.50 per block, the estimated block cost is 1,312.50 in the currency entered. Delivery, tax, mortar, reinforcement and labor are separate.

What this calculator includes—and what it does not

It calculates face-area coverage for concrete masonry units, including an editable allowance, pallets and block-only cost. It does not calculate structural loading, reinforcement, grout, mortar quantities, bond-beam blocks, corner units, lintels, foundations or local code requirements. Complex bond patterns and mixed block sizes should be scheduled separately.

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Frequently asked questions

Does the block dimension include the mortar joint?

Use the nominal face module that repeats across the wall, including the joint. Confirm it with the block supplier or project documents.

How do I account for doors and windows?

Add their face areas and enter the total in the openings field using the selected square unit. The calculator rejects an opening area equal to or larger than the gross wall area.

Should I always add 5% waste?

No. Five percent is only an editable example. Cuts, breakage, bond pattern, site handling and supplier return policy affect the allowance.

Does this calculate mortar or grout?

No. Mortar and grout depend on block geometry, joint thickness, wall thickness, reinforcement and whether cells are filled.

Can I use it for different block sizes?

Yes. Enter the nominal length and height of the repeating face module. Calculate separate wall sections when multiple block sizes are used.

Why is the result rounded up?

Blocks and pallets are discrete items. Rounding upward prevents a fractional item from understating the order quantity.