Formula used
Wall-face area equals total section length multiplied by height. Each section is calculated separately. Their areas are then added together.
Base blocks equal wall-face area divided by block-face area. The result always rounds upward. Corners, cuts, waste, and extras follow afterward.
Courses equal maximum wall height divided by block height. The calculator rounds partial courses upward. Supplier dimensions should confirm the final course count.
Base gravel equals trench length times width times depth. A compaction percentage increases ordering volume. Drainage gravel uses the same volume method.
Geogrid area equals wall length times embedment length times layers. Layers depend on selected vertical spacing. Engineering designs always override calculator estimates.
Total cost combines materials, labour, delivery, equipment, contingency, and tax. Disabled items contribute zero cost. Local prices should replace every default amount.
How to use
- Select imperial or metric measurements.
- Enter each wall section length and height.
- Enter the manufacturer’s block and cap dimensions.
- Add corner, end, cutting, and waste allowances.
- Set base, drainage, fabric, geogrid, and excavation inputs.
- Replace default costs with current supplier quotations.
- Calculate, review warnings, then export the results.
Example data
| Input | Imperial example | Metric example |
|---|---|---|
| Wall length | 30 ft | 9.15 m |
| Wall height | 4 ft | 1.22 m |
| Block face | 16 × 6 in | 40 × 15 cm |
| Base trench | 24 × 6 in | 60 × 15 cm |
| Drainage zone | 12 in wide | 30 cm wide |
| Waste allowance | 7% | 7% |
| Geogrid spacing | 24 in | 60 cm |
Frequently asked questions
How many retaining wall blocks do I need?
Divide wall-face area by one block’s visible face area. Then add corners, cuts, and waste. This calculator completes those steps automatically for you.
What waste percentage should I use?
Five to ten percent suits many straightforward walls. Complex curves may require more. Confirm waste with your chosen block supplier.
Does the calculator include buried blocks?
The entered wall height controls calculated wall-face area. Include buried courses within that height. Manufacturer installation guides determine required embedment depth.
How deep should the gravel base be?
Many systems use a compacted granular base. Depth depends on soil and loading. Follow local codes and manufacturer installation instructions.
When is geogrid required?
Geogrid requirements depend on height, slope, soil, and surcharges. Taller walls often need engineering. Never rely only on this calculator.
Why are corner blocks counted separately?
Corners often use special units or alternating layouts. Their quantities depend on courses. Separate counting improves ordering accuracy.
Can I calculate stepped walls?
Yes, enter stepped portions as separate wall sections. Each section receives its own area. The calculator combines all sections afterward.
How are pallets calculated?
Total blocks divide by blocks supplied per pallet. Partial pallets round upward. Verify pallet quantities with the supplier.
Does excavation equal removed soil?
Excavation is a planning estimate for disturbed ground. Actual disposal may differ considerably. Soil bulking can increase hauled volume.
Can I use supplier prices?
Yes, replace every default cost with current quotations. Keep units consistent when entering prices. The calculator totals selected cost categories.
Is this calculator an engineering design?
No, it provides preliminary material and cost estimates. It cannot assess soil stability. Qualified professionals should design critical retaining walls.
Safety and engineering disclaimer
Retaining walls can fail from poor drainage, weak soils, surcharges, or inadequate reinforcement. Local permits and engineered plans may be required. Verify every result before construction begins.