Calculator
Example data table
| Scenario | Inputs | Perimeter | Coverage per unit | Units to buy |
|---|---|---|---|---|
| Site fence run | Rectangle 30 m × 18 m, waste 5% | 96.000 m | 25.000 m per roll | 5 rolls |
| Sealant around slab edge | Custom segments: 12, 7.5, 6, 4.25 m, waste 8% | 29.750 m | 12.000 m per tube | 3 tubes |
| Round tank base edging | Circle diameter 6 m, waste 3% | 18.850 m | 10.000 m per strip | 2 strips |
Formula used
- Rectangle: P = 2(L + W)
- Circle: P = 2πr or P = πd
- Regular polygon: P = n × s
- Segments: P = Σ segment lengths
- Net: Pnet = max(0, P − D)
- Adjusted: Padj = Pnet × (1 + waste%/100)
- Units: U = Padj ÷ coverage
- Cost: Total = Ubuy × unit_cost
How to use this calculator
- Select a single input unit for the project.
- Choose the shape that matches your perimeter.
- Enter dimensions or segment lengths for the layout.
- Add deductions for gates, openings, or excluded runs.
- Set waste allowance and your material coverage rate.
- Enter unit cost and enable rounding if required.
- Press Submit to see results above the form.
- Download CSV or PDF for records and sharing.
Perimeter inputs for common site layouts
The calculator supports rectangles, circles, regular polygons, and custom segment runs. A 30 m by 18 m rectangle returns 96.000 m, while a 6 m diameter circle returns about 18.850 m. For regular shapes, perimeter follows n × s, so an 8‑sided layout with 2.5 m sides totals 20.000 m. Segment mode fits irregular boundaries such as curb lines, trench edges, or phased fence lines, and it sums every entered length.
Accounting for openings and excluded edges
Deductions remove lengths that should not receive material, such as vehicle gates, door thresholds, or temporary access gaps. Enter the total excluded length once, and the net perimeter is clamped at zero to prevent negative results. For example, 96 m perimeter with 7.2 m deductions produces 88.800 m net before waste.
Coverage rate selection for materials
Coverage per unit is the usable length one item provides, like 25 m per roll, 3 m per board, or 12 m per tube. Use the same unit as your inputs to avoid confusion. When switching units, the tool converts internally to meters and then displays results back in your chosen unit. If your installation needs overlaps, input the effective coverage after overlap, not the label length, to keep quantities realistic.
Waste allowance and rounding strategy
Waste compensates for overlaps, splice losses, corners, and trimming. A 5% allowance multiplies the net perimeter by 1.05; an 8% allowance multiplies by 1.08. Enable rounding when products must be bought as whole items, and keep it off when you are ordering bulk by continuous length.
Costing, purchasing, and record exports
If unit cost is provided, total cost equals units to buy multiplied by unit cost, in your preferred currency. Pair the notes field with line item identifiers, zones, or specifications to keep estimates traceable. Store each run as a separate record. Export CSV for spreadsheets and PDF for sharing with supervisors, vendors, and quantity survey files.
FAQs
1) What does coverage per unit mean?
Coverage per unit is the length one item can cover after your installation method. Enter the effective length in the same unit as your dimensions, so the calculator can divide the adjusted perimeter by that value.
2) When should I use custom segments?
Use custom segments for irregular boundaries or when you measured each side separately. Paste values separated by commas, spaces, or new lines, and the tool will sum them into one perimeter.
3) How do deductions affect the result?
Deductions subtract excluded lengths such as gates, openings, or gaps. The calculator subtracts deductions from the perimeter, then applies waste to the remaining net length, preventing negative results.
4) Should I enable round up?
Enable round up when products are sold only as whole items, like rolls or boards. Leave it off when purchasing by continuous length or when fractional quantities are acceptable in your workflow.
5) How do I choose waste percentage?
Pick waste based on geometry and handling: straight runs need less, while many corners and splices need more. Start with 5%, then test 3% and 10% to see how sensitive your purchase quantity becomes.
6) Can I estimate cost in different currency?
Yes. Unit cost is a numeric input, so you can enter any currency amount. The total cost is units to buy multiplied by unit cost, and it will match whatever currency you used.