Blockwork Cost Calculator

• Gross wall area: Area = Length × Height.
• Net wall area: Net = Gross − Openings (area or percent).
• Blocks per m²: 1 ÷ ((BlockLength + Joint) × (BlockHeight + Joint)).
• Blocks quantity: ceil(NetArea × BlocksPerM² × (1 + BlockWaste%)).
• Wall volume: NetArea × WallThickness.
• Block solid volume: BlockVol × SolidFraction × BlocksRaw.
• Mortar volume: max(0, WallVol − BlockSolidVol) × (1 + MortarWaste%).
• Direct cost: Materials + Delivery + Labor + Add-ons + Lumps.
• Overhead: Direct × Overhead%.
• Profit: (Direct + Overhead) × Profit%.
• Tax: (Direct + Overhead + Profit) × Tax%.

1. Enter wall length and height using your chosen unit.
2. Deduct doors and windows using area or percent.
3. Set block size, joint thickness, and realistic waste factors.
4. Update unit costs for blocks, mortar, and delivery.
5. Select a labor method: per m² rate, or hourly productivity.
6. Enable add-ons like scaffolding, reinforcement, or plaster as needed.
7. Apply overhead, profit, and tax percentages to match your bid structure.
8. Press Calculate and export the breakdown as CSV or PDF.

Blockwork estimates change fastest when geometry and rates move together. Net wall area is the main multiplier, but openings, joint thickness, and block format also shift quantities. This calculator converts inputs to metric internally, then applies consistent formulas for blocks, mortar volume, labor, and markups. Use it for budgeting, tender comparisons, and checks during revisions. For better accuracy, enter rates, wastage, and a labor method suited to your crew.

Wall area, openings, and thickness

Gross area equals wall length times height. Openings can be deducted by total area or by percentage, which is useful when drawings are not finalized. Wall thickness is taken from the selected block thickness and drives wall volume, which supports mortar estimation and explains cost differences between 100 mm and 200 mm work.

Block count from module size

Blocks per square meter are calculated using the effective module: (block length plus joint) by (block height plus joint). Changing block size or joint thickness changes coverage. Waste is applied after the raw count and rounded up to whole units for procurement, giving a practical order quantity.

Mortar volume using solid fraction

Mortar volume is estimated as wall volume minus the total solid block volume. The solid fraction represents how much of a hollow unit is concrete, commonly 0.45 to 0.65. This method adapts to different block types and reduces overestimation compared with assuming the wall is fully solid.

Labor, add-ons, and delivery

Labor can be priced as a simple rate per square meter, or as hourly cost using productivity. Optional add-ons such as scaffolding, reinforcement, and plaster are included as separate lines so scope changes remain transparent. Delivery is applied as a percentage of material costs to reflect handling and haulage variation.

Overhead, profit, and tax structure

After direct costs are summed, overhead is applied first, then profit is calculated on direct plus overhead. Tax is applied last. This sequence mirrors common estimating practice and keeps comparisons consistent when overhead policies or profit targets differ between bidders.

1) How do I choose openings by area or percent?

Use area when you know door and window sizes. Use percent during early design when only a typical deduction is available. Openings are capped so they cannot exceed gross wall area.

2) What solid fraction should I use for hollow blocks?

Start at 0.55 for common hollow concrete blocks. Use 0.45–0.50 for lighter units with larger voids, and 0.85–0.95 for solid units. Adjust if your supplier provides test data.

3) Why does joint thickness affect block quantity?

Coverage is based on the module size: block dimensions plus joint thickness. Larger joints increase the module area per unit and can reduce blocks per square meter, while also influencing mortar volume.

4) When should I use hourly labor with productivity?

Choose hourly when access, staging, or scaffolding moves affect output. Productivity-based labor helps you model constrained sites. Use recent project performance to set realistic square meters per hour.

5) Do waste percentages change cost or just quantities?

They affect both. Block waste increases the purchase quantity, and mortar waste increases the estimated volume. Because materials are priced from these adjusted quantities, the total cost responds directly to waste settings.

6) What is included in the exported CSV and PDF?

The CSV exports the cost breakdown table for spreadsheets. The PDF includes a summary and the same breakdown in a print-ready format. Confirm inclusions such as plaster, reinforcement, and scaffolding before sharing externally.