CalcCalculatrice Mur de Soutènement
Dernière mise à jour: 2026-05-07
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| Longueur du mur (m) | Longueur du bloc (cm) | Hauteur du bloc (cm) | Hauteur du mur (m) | |
|---|---|---|---|---|
| Small wall | 3 m | 20 cm | 0.2 cm | 0.9 m |
| Medium wall | 4.5 m | 20 cm | 0.2 cm | 0.9 m |
| Large wall | 6 m | 20 cm | 0.2 cm | 0.9 m |
| Room | 9 m | 20 cm | 0.2 cm | 0.9 m |
| House perimeter | 12 m | 20 cm | 0.2 cm | 0.9 m |
What is the Retaining Wall Calculator?
Retaining walls hold back soil on sloped sites — and building one without enough drainage or structural blocks leads to wall failure and costly repair. This calculator computes the total number of concrete blocks needed for your wall dimensions, plus the volume of drainage gravel to place behind the wall for water management.
You may also find the Concrete Steps Calculator, Drywall Calculator, and Paver Calculator useful.
Who Uses This Calculator?
This tool is used by homeowners landscaping a sloped yard, landscapers building garden retaining walls, and civil engineers specifying low-height retaining structures.
How to Use the Retaining Wall Calculator
- Enter your Wall length.
- Enter your Wall height.
- Enter your Block length.
- Enter your Block height.
- Click Calculate to see your results instantly.
Formula
The calculator uses the following formula:
Blocks = ceil(length ÷ block_L) × ceil(height ÷ block_H); Gravel = length × base_depth × 0.6
Worked Example
A 6 m long × 0.9 m high retaining wall using 400 mm × 200 mm blocks needs approximately 68 blocks plus 1.08 m³ of drainage gravel behind it.
Step-by-Step Calculation
- Courses high: ceil(0.9 m ÷ 0.2 m) = 5 courses
- Blocks per course: ceil(6 m ÷ 0.4 m) = 15 blocks
- Total blocks: 15 × 5 = 75 blocks
- Base gravel depth: 20 cm; Volume: 6 × 0.6 × 0.2 = 0.72 m³ ≈ 1.1 tonnes
Common Mistakes to Avoid
- Not burying the first course below grade — minimum 10% of wall height
- Forgetting drainage pipe and gravel backfill behind the wall
- Using standard blocks instead of approved retaining wall blocks for walls > 90 cm
Frequently Asked Questions
Most councils allow retaining walls up to 600–900 mm high without engineering certification. Walls above 1 m typically require a structural engineer's design and council approval. Always check local regulations.
Concrete segmental retaining wall blocks (SRW blocks) are the most common for DIY. They interlock without mortar and are designed for retaining walls. Sizes typically range from 200 × 100 × 200 mm to 450 × 200 × 250 mm.
A batter of 1:10 (10 mm per 100 mm of height) is standard for segmental block walls. This lean-back improves stability by shifting the wall's centre of gravity toward the retained soil.
Use clean 20 mm crushed rock or gravel (no fines). Fines compact and retain water, defeating the purpose. The drainage layer should be at least 300 mm wide, wrapped in geofabric to prevent soil ingress.
This depends on block height. 200 mm blocks give 5 courses per metre, 100 mm blocks give 10 courses per metre. Calculate: height (mm) ÷ block height (mm) = number of courses.