| Use case | Shape | Measured size | Fit | Recommended cover size |
|---|---|---|---|---|
| Raised bed frame | Rectangular | 120 × 60 × 50 cm | Standard | ~128 × 68 × 53 cm |
| Round planter | Round | Diameter 80 cm, Height 70 cm | Loose | ~92 × 73 cm |
| Patio table cover | Oval | 160 × 90 × 75 cm | Standard | ~170 × 100 × 78 cm |
- Recommended dimensions = measured dimensions + 2 × fit allowance (length/width/diameter) and + extra height.
- Cut size adds seam allowance on both sides and hem/bottom finish.
- Rectangular surface area ≈ top (L × W) + sides (2 × (L+W) × H).
- Round surface area ≈ top (πr²) + sides (πD × H).
- Oval surface area uses ellipse area (πab) and Ramanujan perimeter approximation for the sides.
- Fabric needed = surface area × (1 + waste%) ÷ (1 − shrink%).
- Select your unit and the object’s shape.
- Measure the maximum outer length, width, and height (or diameter).
- Choose a fit style. Use custom allowance for exact preferences.
- Adjust seam, hem, extra height, and tie spacing as needed.
- Press Calculate to view results above the form.
- Download CSV or PDF for your project notes.
Sizing for Weather and Drainage
Outdoor covers should shed rain and leave room for airflow. A cover that is too tight traps moisture against soil, wood, and metal. For raised beds and small frames, add enough allowance to keep fabric off foliage and prevent abrasion on corners. If the item sits on uneven ground, include extra height so the hem clears rocks and edging. For long runs, measure twice, then round to the nearest available cover size to avoid custom ordering and returns during busy seasons.
Fit Allowance by Cover Material
Different materials behave differently in the garden. Coated polyester stretches very little, so a standard allowance reduces stress on seams. Knitted fabrics can deform, so a snug allowance may still fit. As a rule, snug is best for indoor storage, standard for most patios, and loose when the cover must slip over handles, rails, or bulky plant growth.
Seam, Hem, and Secure Height Planning
Cut size is not the same as the final cover size. Seam allowance adds material for stitching, while hem allowance supports a fold, elastic, or drawstring channel. Extra height for securing creates a skirt that can be tucked under a pot lip or tied below a tabletop. In windy locations, increase secure height and choose more tie points rather than oversizing the top.
Surface Area and Fabric Estimation
The calculator estimates surface area so you can budget fabric and coatings. Rectangular and round shapes use standard top-plus-sides formulas, and oval shapes use an ellipse area with a proven perimeter approximation. Waste factor accounts for offcuts and pattern alignment, while shrinkage prevents undersized results after stitching or heat bonding.
Tie-Down Layout and Wind Readiness
Tie-down points are estimated from the bottom perimeter and your spacing input. Closer spacing reduces flapping, protects seams, and helps the cover stay centered. Use webbing loops at corners first, then distribute the remaining points evenly. For tall, narrow items, add a mid-height strap to control ballooning.
FAQs
1) Which measurements matter most for irregular garden items?
Measure the maximum length, width, and height, including handles and rims. For irregular profiles, size to the widest points and choose standard or loose fit so the cover clears protrusions without tearing.
2) Is snug fit recommended outdoors?
Snug fit can work in sheltered areas, but it may trap moisture and stress seams. For typical patios and beds, standard is safer. Choose loose when you need clearance for plant growth or bulky features.
3) How do waste and shrinkage change fabric estimates?
Waste adds a buffer for offcuts, pattern matching, and mistakes. Shrinkage protects against tightness after stitching or heat bonding. Increasing either value raises the fabric-needed output, which helps avoid shortages.
4) Why add extra height for securing?
Extra height creates a skirt that can be tucked, cinched, or tied below the item. It improves wind resistance and helps the hem stay below the base edge, especially on uneven ground or raised surfaces.
5) How is tie-down points calculated?
Points are estimated by dividing the bottom perimeter by your tie spacing, then rounding up. Smaller spacing increases points and reduces flapping. Always start with corners, then distribute the remaining points evenly.
6) Can I order a ready-made cover using these results?
Yes, use the recommended size as a target, then match it to a product sizing chart. If your nearest size is between options, select the larger one and rely on cinches or straps for a secure fit.