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Recommended rolls
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Drop length (in)
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Drops per roll: —
Total drops: —
Perimeter (ft): —
| Method | Rolls | Note |
|---|---|---|
| Drop-based | — | Uses strip count and drops per roll |
| Area-based | — | Adjusts coverage by repeat and openings |
Half‑drop alignment visualizer
▲ Top trim / rounding waste
■ Pattern tiles
— Repeat grid lines
In a half‑drop, every second strip starts half a repeat lower, so motifs align diagonally across seams. The visual shows drop length, repeat tiles, and trim waste.
Formula used
- Perimeter (rectangle) = 2 × (Length + Width)
- Perimeter (custom) = Sum of all wall lengths
- Adjusted height (in/cm) = Wall height + Trim allowance
- If repeat > 0: Drop length = ceil(Adjusted height ÷ Repeat) × Repeat; else = Adjusted height
- Half‑drop visual shows offset of half the repeat on alternating drops
- Drops per roll = floor(Roll length ÷ Drop length)
- Total drops ≈ ceil(Perimeter ÷ Roll width)
- Rolls (drop method) = ceil(Total drops ÷ Drops per roll)
- Roll area = Roll width × Roll length (unit-consistent)
- Efficiency ≈ Wall height ÷ Drop length (repeat overhead factor)
- Effective roll area = Roll area × Efficiency × (1 − waste%)
- Recommended rolls = max(drop method, area method) + Minimum extra rolls
How to use
- Select unit system and layout mode.
- For rectangle, enter room length, width, and height.
- For custom walls, list each wall run and count, set height.
- Provide roll width, roll length, pattern repeat, and match type.
- Use the visualizer to preview half‑drop or straight alignment.
- Click Calculate. Export results to CSV or PDF.
Example scenarios
| Layout | Room / Walls | Roll w × L | Repeat / Match | Waste% | Result (approx. rolls) |
|---|---|---|---|---|---|
| Rectangle (US) | 14×12×108 in | 20.5 in × 33 ft | 21 in / Straight | 10% | ~ 8–9 |
| Custom (US) | Walls: 18+10+6+6 ft, H=108 in | 27 in × 27 ft | 13 in / Half-drop | 12% | ~ 9–10 |
| Rectangle (Metric) | 4.5×3.6×270 cm | 52 cm × 10 m | 0 cm / Random | 8% | ~ 6–7 |
Use the sample-fill buttons for quick testing.
What is pattern repeat (inches) and match types?
Pattern repeat is the vertical distance before a motif repeats. When planning drops, the usable drop length must be rounded up to the next whole repeat after adding trim allowance.
- Straight match: Adjacent drops align at the same height; trimming occurs mostly at top and bottom.
- Half‑drop match: Every second drop starts half a repeat lower; diagonal motif alignment increases trimming overhead.
- Random/no match: Motifs don’t require alignment; repeat can be treated as zero for drop rounding.
Drop rounding rule: Drop length = ceil((Wall height + Trim) ÷ Repeat) × Repeat.
If repeat is zero, use Wall height + Trim directly.
Common roll sizes and nominal coverage (no repeat/waste)
| Roll width × length | Area (ft²) | Area (m²) |
|---|---|---|
| 20.5 in × 33 ft | 56.38 | 5.24 |
| 27 in × 27 ft | 60.75 | 5.64 |
| 52 cm × 10 m | 56.00 | 5.20 |
Actual coverage is reduced by the efficiency factor (Wall height ÷ Drop length) and any added waste.
Use this calculator to apply those adjustments automatically.