Retaining Wall Calculator
About Retaining Wall Calculation
The Retaining Wall Calculator helps you plan segmental or landscape block walls in the metric system. Enter wall length, visible height and embedment, block length and height, optional capping course and backfill to get block courses, total blocks, cap pieces, face area, backfill volume and mass, final wall height, and optional costs. The tool also supports block mass by kg/m² or per piece and cost by piece, tonne, or m³.
Use it to answer practical questions such as how many retaining wall blocks you need, how much backfill to order, or to make a quick retaining wall cost estimate before you talk to suppliers or an engineer.
Tips and Tricks
- Measure once, enter once. Set Wall length, Visible height, and Embedment in centimetres. Overall height is calculated as visible height + embedment, while the effective height for blocks excludes the optional cap.
- Typical block sizes. Many concrete retaining blocks are about 30-45 cm long and 10-20 cm high. Choose values that match your product and enter them in Block length and Block height.
- Allow for waste and cuts. Common allowances are 3-7 % for blocks and 2-5 % for caps. Set these in Block allowance and Allowance to avoid shortages.
- Capping course. Tick Add course to include caps. The cap height is added on top of the block courses, while its length is used to count pieces.
- Backfill planning. Tick Calculate backfill and set layer thickness and height (often similar to overall wall height). A drainage layer 20-40 cm thick is commonly used behind small gravity walls; adjust to your design and ground conditions.
| Material | Typical density, kg/m³ |
|---|---|
| Crushed stone | ≈ 1500 |
| Sand | ≈ 1600 |
| Gravel | ≈ 1700 |
| Loam | ≈ 1800 |
- Mass & cost modes. For block weight, choose By m² (enter kg/m² of facing) or By pieces (enter kg per block). For backfill cost, switch between price per tonne and per m³ to match your quote.
- Quick formulas used by the calculator.
- Block courses =
ceil((overall height − cap height) / block height) - Blocks per course =
ceil(wall length / block length) - Total blocks with allowance =
ceil(courses × per-course × (1 + allowance/100)) - Backfill volume (with allowance) =
wall length × backfill thickness × backfill height × (1 + allowance/100)
- Block courses =
- Good practice and norms. Provide drainage and a compacted granular backfill where required. For design and safety, consult local rules and European standards such as EN 1997-1 (Eurocode 7) for geotechnical design and EN 13242 for aggregates.
- When to seek engineering advice. If the wall is high, supports traffic/surcharges, is near property boundaries or poor soils, or uses geogrid/reinforcement, treat this tool as a materials estimator only and consult a qualified engineer.
FAQs
How many retaining wall blocks do I need?
Enter your dimensions and the calculator counts courses and blocks per course, then adds your waste allowance. This answers the classic “how many retaining wall blocks do I need” question without manual math.
Does this work as a retaining wall block calculator for landscape projects?
Yes. It's a landscape block estimator as well as a wall block calculator. Use your actual block size and allowance to estimate pieces for garden terraces, planters, and small gravity walls.
How does the retaining wall cost estimator work?
Enable Cost calculation, enter block and cap prices per piece, and set backfill price per tonne or per m³. The retaining wall cost calculator multiplies the quantities by your prices and shows itemised and total costs.
Does the tool calculate a footing or foundation?
It does not design reinforced concrete footings or structural foundations. The Embedment field simply adds buried height to the block count; any footing design should follow local codes or professional guidance.
What formulas does the retaining wall calculation use for results?
The estimator uses ceiling division based on your block height and length to avoid partial units and reflects allowances you set. Face area (m²), backfill volume (m³), masses (kg) and final wall height (cm) are computed directly from the entered metric values.