Calculator inputs
Designed for garden spaces like sunrooms, greenhouse bays, and potting sheds.
Formula used
1) Effective finished size
Inside mount uses your finished width and length. Outside mount adds overlap: effective width = finished width + 2 × side overlap, and effective length = finished length + top overlap.
2) Stack allowance
Stack is the extra fabric needed for folds when the shade is raised. You can use a percent rule or enter a custom inches value.
3) Cut panel size
cut width = effective width + 2 × side hem
base cut length = effective length + top allowance + bottom hem + stack
4) Pattern repeat rounding
If vertical repeat is greater than zero, the cut length is rounded up:
cut length = ceil(base cut length ÷ repeat) × repeat.
5) Total yardage
Drops per shade: drops = ceil(cut width ÷ fabric width).
Total inches: total = drops × cut length × quantity.
Waste: total_with_waste = total × (1 + waste%).
Convert to yards: yards = total_with_waste ÷ 36.
How to use this calculator
- Measure the finished width and length of each garden window opening.
- Pick inside or outside mount, then set overlap values if outside.
- Enter your fabric width, hem allowances, and top/bottom allowances.
- Add stack allowance using percent or your measured stack height.
- If your fabric has a pattern, enter the vertical repeat to match prints.
- Choose lining options, then add costs if you want a price estimate.
- Press Calculate to view the cut size, drops, and total yardage above.
- Use the download buttons to save a worksheet for shopping or records.
Example data table
| Scenario | Finished size (W×L) | Fabric width | Repeat | Shades | Result highlight |
|---|---|---|---|---|---|
| Greenhouse side window | 28 in × 48 in | 54 in | 0 in | 2 | Simple solids with lining for sun control |
| Sunroom picture window | 40 in × 72 in | 60 in | 12 in | 1 | Repeat rounding increases cut length |
| Potting shed door glass | 20 in × 36 in | 45 in | 6 in | 3 | Small panels; waste % matters for multiples |
Examples show typical setups; your actual yardage depends on allowances, stack choice, and print matching needs.
Fabric planning for garden-facing windows
Roman shades are common on greenhouse, potting-shed, and sunroom windows because they control glare without blocking airflow. This calculator converts window measurements into cut sizes, then into total yardage so you can buy fabric once and avoid mid-project dye-lot issues. For garden spaces, measure at three points to capture frames that swell with humidity. Use the largest value for steady coverage.
Allowances that affect real yardage
Side hems, top allowances, and bottom hems are small numbers that add up. For example, adding 1.25 in side hems on both sides increases cut width by 2.5 in. On narrower fabrics this can push you from one drop to two. The tool shows drops per shade using your fabric width, making it easier to see when a small design choice changes purchase quantity.
Stack height and plant-safe light control
Stack height is the folded bundle when the shade is raised. A typical 15–25% stack keeps the shade compact while preserving top-of-window light for seedlings. Choosing a larger stack gives deeper folds and stronger blackout performance when you start seeds under controlled light. The calculator lets you use a percent rule or a custom stack if your hardware or fold depth is fixed.
Pattern repeat and seam matching
Printed fabrics require repeat rounding so motifs align. If the vertical repeat is 12 in and your base cut length is 86 in, rounding raises it to 96 in. That extra 10 in can be the difference between having enough fabric and coming up short. Use the repeat field to protect your layout, especially for botanical prints used in garden rooms.
Lining choices for heat and moisture
Lining can reduce fading and help stabilize temperature near plants. A light-filtering lining is enough for bright patios, while blackout lining suits media corners or heat-sensitive plants. Because lining is a different width, the calculator estimates lining yardage separately using your lining width and allowances, and then applies an optional waste percentage for ordering.
FAQs
What is a “drop” in the results?
A drop is one fabric panel cut to the shade length. Drops per shade are calculated from cut width and fabric width. If the shade is wide, you may need multiple drops joined with seams.
Should I measure inside or outside the frame?
Use inside mount for a cleaner look within the frame; outside mount covers more light gaps. The calculator supports both by adjusting effective width and length with your chosen overlap values.
How do I choose a waste percentage?
Use 5–10% for solids and simple cuts. Use 10–20% for prints, biasing, or when multiple small shades share one bolt. Extra waste is also helpful when you’re new to sewing.
Do I need to enter vertical repeat for solid fabrics?
No. Leave repeat as 0 for solids or textures without a directional pattern. Repeat rounding is only applied when the vertical repeat is greater than zero.
Why does lining yardage differ from face fabric?
Lining is often narrower or wider than the decorative fabric and may use different allowances. The tool estimates lining with its own width and hem settings, so you can buy the correct amount.
Will this include rings, dowels, or mounting hardware?
No. The estimate is for fabric and optional lining only. Hardware and lift components vary by system and fold spacing, so treat those as separate bill-of-materials items.