Calculator
Example data table
| Wall length | Wall height | Spacing | Embedment | Roll (W×L) | Waste | Estimated layers | Estimated rolls |
|---|---|---|---|---|---|---|---|
| 40 ft | 4 ft | 2 ft | 4 ft | 4 ft × 150 ft | 8% | 3 | 1 |
| 20 m | 1.8 m | 0.6 m | 2.4 m | 4 m × 50 m | 10% | 4 | 2 |
Examples are illustrative; your design may require different spacing, lengths, and overlaps.
Formula used
- Estimated layers = ceil(Wall height ÷ Vertical spacing) + (optional top layer)
- Cut length per layer = Embedment length + Front wrap allowance
- Base area = Layers × Wall length × Cut length
- Seams per layer = max(0, ceil(Wall length ÷ Roll width) − 1)
- Overlap area = Layers × Seams per layer × Overlap length × Cut length
- Total area = (Base area + Overlap area) × (1 + Waste%/100)
- Rolls needed = ceil(Total area ÷ (Roll width × Roll length))
Cost totals include material, optional labor, delivery, contingency, and tax.
How to use this calculator
- Select your units and enter wall length and height.
- Set vertical spacing based on your wall design.
- Enter embedment length and any front wrap allowance.
- Add overlap length and a waste factor for realistic ordering.
- Enter roll width and length from your product label.
- Choose pricing and labor modes, then add delivery and tax.
- Click Calculate to view area, rolls, and full cost breakdown.
- Use the CSV or PDF buttons to save the estimate.
Professional article
Geogrid role in reinforced walls
Geogrid adds tensile reinforcement to compacted backfill, helping a retaining wall resist sliding and overturning while controlling outward bulging. For garden walls, reinforcement is common as heights rise and soils become less predictable. Estimating layers and coverage early reduces change‑orders and supports better material planning.
Layer spacing and count planning
Many segmental systems place geogrid every 0.6 m to 0.8 m (about 2 to 2.5 ft) in height, but spacing is set by the design. This calculator estimates layers using wall height divided by vertical spacing, then optionally adds a top layer when cap details or surcharge loads exist.
Embedment length and connection allowance
Embedment length is the geogrid distance extending back into the reinforced zone. Designers may specify lengths tied to wall height, soil strength, and site loads. Add a front wrap or connection allowance to capture the extra material needed to engage the facing, wrap around units, or reach mechanical connectors.
Overlaps, seams, and roll layout
On each layer, geogrid panels are often placed with the roll width running along the wall length. If the wall is longer than roll width, seams occur. The calculator estimates seams as the number of panels minus one, then adds overlap area using your overlap length to avoid under‑ordering on long runs.
Waste factor for realistic ordering
Cutting around steps, corners, posts, and tight radii creates off‑cuts that cannot always be reused. Installation damage and field adjustments also add loss. A waste factor of 5% to 12% is common for straightforward layouts, while complex geometry may justify higher values to keep crews productive.
Roll optimization and purchasing strategy
Roll area equals roll width multiplied by roll length. The calculator converts total required area into a roll count using ceiling rounding, which mirrors purchasing reality. To reduce leftover material, compare alternative roll sizes, consider standardizing embedment lengths across tiers, and plan layer breaks where transitions minimize seams.
Cost drivers and budgeting inputs
Material cost can be priced per roll or per area, matching supplier quotes. Labor can be modeled per area, per roll, or excluded for owner‑built projects. Delivery, contingency, and tax complete the estimate. Access constraints, compaction effort, and wall alignment quality are common drivers of labor variability. Also coordinate delivery with staging space.
Field verification checklist before ordering
Confirm wall length along the actual face alignment, including curves and returns. Verify finished height from base to top of cap, then confirm vertical spacing from the design. Check embedment length against property lines and utilities, and confirm roll dimensions from the product label. Re‑run the calculator after layout changes.
FAQs
Q: What does the calculator output?
A: It estimates geogrid layers, total coverage area, rolls required, and a cost breakdown including material, labor, delivery, contingency, tax, and a grand total.
Q: How is the number of layers estimated?
A: Layers are calculated as the ceiling of wall height divided by vertical spacing. You can add one extra top layer if you want a conservative estimate for caps or surcharges.
Q: Should roll width match wall length direction?
A: Most installations run roll width along the wall face and cut strips to the embedment length. If your layout differs, adjust roll dimensions and overlap assumptions to reflect how panels will be placed.
Q: How do overlaps affect quantity?
A: When the wall length exceeds roll width, seams occur. Overlap length adds extra area at each seam for each layer, which reduces the risk of ordering short on long walls.
Q: What waste factor should I use?
A: Use 5–12% for simple straight walls. Increase it for steps, corners, curves, limited access, or frequent cutoffs. A higher waste factor can prevent delays caused by missing material.
Q: Can I price by area instead of roll?
A: Yes. Choose “price per area” when your supplier quotes cost per square unit. Choose “price per roll” when you purchase full rolls and want the total based on roll count.
Q: Is this a final engineering design?
A: No. It is a planning estimate. Always follow your engineered wall design, product specifications, and local requirements for reinforcement spacing, embedment length, drainage, and compaction.
Use these estimates to plan safer wall reinforcement properly.