Calculator
Example data table
| Scenario | Inputs | Outputs |
|---|---|---|
| Beds | 4 beds, 2.4×1.2 m, overlap 5%, waste 10%, roll 0.45×30 m | Base area 11.52 m², adjusted 13.30 m², length 29.56 m, rolls 1 |
| Pots | 12 pots, 0.30 m diameter, cover only, overlap 5%, waste 10%, roll 0.30×20 m | Base area 0.85 m², adjusted 0.98 m², length 3.28 m, rolls 1 |
| Paths add-on | Paths 10×0.5 m added to beds example | Base area +5.00 m², adjusted increases accordingly, rolls may rise |
Formula used
- Beds area: A = beds × length × width
- Pots top area: A = pots × π × (diameter/2)²
- Pots lining (optional): A = pots × (2πr) × depth
- Paths (optional): A = length × width
- Adjusted area: Aᵃ = A × (1+overlap%) × (1+waste%)
- Foil length needed: L = Aᵃ ÷ roll_width
- Rolls required: R = ceil(L ÷ roll_length)
How to use this calculator
- Select your unit system and coverage type.
- Enter roll width and roll length from the packaging.
- Fill bed sizes or pot dimensions, then set overlap and waste.
- Optionally add path coverage and cost per roll.
- Press Estimate foil usage to see results above the form.
- Download CSV or PDF to save your plan.
Selecting Foil for Garden Tasks
Reflective foil sheets can boost light around seedlings, while heavy-duty foil works for temporary soil covers and compost lids. Choose food-safe foil only for indirect contact, and use thicker grades where wind or foot traffic is expected. Wider rolls reduce seams, but narrower rolls fit raised beds and containers with less trimming. For light reflection, face the shiny side toward plants and keep it clean so it stays bright and effective longer.
Measuring Beds, Pots, and Path Runs
For rectangular beds, measure the usable planting surface, not the outside frame. For pots, a circular top cover uses diameter, and optional side lining adds the pot’s circumference times depth. Long rows or walkways are easiest as one combined length and width, then treated as an extra area add-on. Measure bed corners twice, then average if sides bow; this prevents underbuying on irregular frames.
Planning Overlap and Waste Allowance
Overlap protects edges from lifting and keeps light-blocking barriers continuous. A small overlap suits flat beds, while higher overlap helps uneven soil, curved planters, or windy sites. Many gardeners start with 5–10% overlap and 8–15% waste, then adjust after a trial run. Waste accounts for cutouts around stems, tears, and misaligned strips. When securing edges with soil or staples, overlap can be slightly lower without gaps forming.
Converting Area to Roll Length
The calculator converts your adjusted coverage area into a required length by dividing by roll width, assuming straight, parallel strips. If your layout uses diagonal pieces or frequent cut-and-fit sections, real consumption rises. Compare the required length to your roll length, then round up to whole rolls so you can finish without patchwork. If you cut many openings, treat each as extra waste.
Budgeting and Practical Handling Tips
Cost per roll turns material totals into a simple budget, useful when comparing brands or thickness. Store rolls indoors to prevent edge damage and oxidation, and cut on a clean board for accurate lengths. Anchor foil with landscape staples, boards, or soil at the edges, and remove fragments after use to keep beds tidy. For reuse, clean and reroll. Label rolls with unit system.
FAQs
1) What overlap percentage should I start with?
Start with 5–10% for flat beds. Increase overlap when soil is uneven, edges must wrap, or wind is strong. More overlap improves sealing but raises roll length requirements.
2) How do I estimate foil for circular pots?
Use pot diameter for the top cover. If you line the sides, add circumference times depth. The calculator combines both so you can compare rolls quickly.
3) Why does roll width change the required length?
Coverage area stays the same, but wider material covers more area per meter or foot of length. Dividing area by roll width converts area into a practical strip length.
4) Should I include paths and rows?
Include them when you plan to block weeds or reflect light between beds. Measure total length and width, add it as an extra area, and the calculator will adjust rolls accordingly.
5) What waste allowance is realistic?
8–15% is common for trimming and cutouts. Use higher waste for complex shapes, frequent plant openings, or first-time installs. Reduce waste after you learn your cutting pattern.
6) Does this estimate account for thickness or tearing?
No. Thickness affects durability, not coverage math. If you expect punctures or rework, increase waste or buy an extra roll for safety.