Row Cover Fabric Calculator

Calculator

Formula used

How to use this calculator

1. Pick your units and choose a width method.
2. Enter row length and the number of rows to cover.
3. For direct width, fill bed width and side drops, or set an override.
4. For hoop width, enter hoop span and rise, plus edge allowance.
5. Set roll width and overlap if your cover needs multiple panels.
6. Add waste, price, and gsm if you want cost and weight estimates.

Measure the protected footprint

Start with the actual row length that needs protection, not the full bed length. Include access gaps near paths and irrigation manifolds. A common garden row is 6–18 m, but tunnels often run longer. Enter row count so the calculator multiplies pieces correctly. Plan cuts early.

Choose a width method that matches your frame

For flat drape covers, the direct method works well: bed width plus two edge drops. For hoop tunnels, the hoop method estimates the arc using a half‑ellipse approximation, then adds edge allowance for anchoring. Many tunnels span 0.9–1.5 m. If your frame is irregular, use the width override and enter the measured fabric span.

Account for seams when rolls are narrow

Many covers exceed common roll widths, especially insect netting and heavy frost cloth. When required cover width is larger than roll width, the tool adds panels across the bed. It subtracts overlap between panels to maintain the target width after seaming. Typical overlaps range from 10–20 cm, depending on stitching, tape, or clips used. Wider rolls reduce seams.

Use allowances to reduce failures in wind

End allowance supports burying edges, adding tie‑downs, or folding a hem for grommets. Edge allowance and side drops help keep fabric sealed against pests and drafts. Many growers use 20–40 cm on each end and 10–20 cm on each side, then adjust for terrain. For windy sites, increase allowances and add a higher waste factor to avoid mid‑row shortages.

Translate length and area into cost and handling

Linear length is what you buy from a roll, while area reflects fabric mass and coverage. Add price per meter to estimate spend and compare roll options quickly. If you enter fabric gsm, the calculator estimates total weight for storage and setup planning. Lightweight covers deploy fast, but heavier grades resist abrasion and UV longer. Use results to order one extra meter per roll for repairs and field adjustments.

FAQs

1) What overlap should I use for multi-panel covers?

Use 10–20 cm for stitched seams, and 15–25 cm for taped seams. If you rely on clips, choose the higher end so the seam stays closed under tension.

2) Should I pick direct or hoop width for low tunnels?

Choose hoop width if fabric sits over a curved frame. Choose direct width for flat drape covers or when you measure the span manually and prefer to override.

3) Why does total length increase when I add waste?

Waste accounts for trimming, alignment errors, damaged sections, and offcuts near seams. A small percentage can prevent shortages that stop installation mid‑row.

4) Does overlap reduce the amount of fabric I buy?

No. Overlap reduces effective finished width, but you still purchase full roll width for each panel. The calculator keeps overlap so the combined width meets the requirement.

5) How do I estimate weight if my supplier uses oz/yd²?

Convert to gsm first, then enter gsm. A quick method is to use a converter or supplier sheet, because weight varies by weave and coating.

6) What if my ends are gathered instead of capped?

Increase end allowance to cover gathering and tie‑off. For drawstring ends, add extra length so the fabric can bunch without pulling the cover off the row.

Example data table