Inputs
White theme
Results
Room area
—
sq ft
Coverage width used
—
ft
Plain design
Drops needed—
Total cut length—
Area used—
Waste area—
Waste percentage—
With extra allowance—
Estimated material cost—
Patterned design
Drops needed—
Total cut length—
Area used—
Waste area—
Waste percentage—
With extra allowance—
Estimated material cost—
Comparison delta:
Across-width repeat rounds coverage width to the next multiple of the repeat to approximate edge alignment. Half-drop match alternates drop lengths to maintain motif continuity.
Extra waste vs plain: —
Waste percentage difference: —
Estimated extra cost: —
Formula used
Plain design
drops_plain = ceil(room_width / roll_width) cut_length_plain = room_length total_length_plain = drops_plain * cut_length_plain area_used_plain = total_length_plain * roll_width waste_plain = area_used_plain - (room_length * room_width) waste_pct_plain = waste_plain / (room_length * room_width) * 100
Patterned design
coverage_width_needed = repeatW > 0 ? ceil(room_width / repeatW) * repeatW : room_width drops_pat = ceil(coverage_width_needed / roll_width) // Straight match drop_len_A = (repeatL > 0) ? ceil(room_length / repeatL) * repeatL : room_length // Half-drop match drop_len_B = (repeatL > 0) ? ceil((room_length + 0.5*repeatL) / repeatL) * repeatL : room_length if matchType == "straight": total_length_pat = drops_pat * drop_len_A else: odd = ceil(drops_pat/2); even = floor(drops_pat/2) total_length_pat = odd*drop_len_B + even*drop_len_A area_used_pat = total_length_pat * roll_width waste_pat = area_used_pat - (room_length * room_width) waste_pct_pat = waste_pat / (room_length * room_width) * 100
Then an extra on-site allowance (%) is applied to the used area for both designs. Cost estimates multiply area (with allowance) by the cost per unit area when provided.
How to use this calculator
- Choose units and enter the room length and room width.
- Enter the roll width supplied by the mill or retailer.
- For patterned goods, enter the pattern repeat lengthwise and across-width. Leave zero to simulate a plain design.
- Select the match type: straight or half-drop.
- Add an extra allowance percentage to cover site realities (cuts, trimming, mistakes).
- Optionally, add a material cost per unit area to compare budget impact.
- Click Calculate to see drops, total cut length, used area, waste, and percentages, side by side.
- Export the outcome via the CSV or PDF buttons or load a preset from the examples below.
Example scenarios
Load any row to prefill the form.
| # | Units | Len | Width | Roll | Repeat L | Repeat W | Match | Extra % | Description | Action |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | ft | 18 | 13 | 12 | 0 | 0 | straight | 5 | Plain benchmark for a mid‑sized room | |
| 2 | ft | 18 | 13 | 12 | 1.5 | 1.0 | straight | 7 | Medium repeat both directions | |
| 3 | ft | 22 | 17 | 15 | 2 | 0 | half | 6 | Large room with half‑drop motif | |
| 4 | m | 5.5 | 4.4 | 4 | 0.3 | 0.2 | straight | 5 | Metric project with tight repeat | |
| 5 | ft | 12 | 24 | 12 | 1 | 2 | half | 8 | Wide room requiring multiple drops and alignment | |
| 6 | m | 6.2 | 3.7 | 5 | 0 | 0 | straight | 4 | Metric plain with wide roll |
FAQs
- Why does a patterned design often require more material?
- Patterns must align at seams and edges. The calculator rounds cut lengths to pattern repeats and coverage width to repeat multiples, which increases total material compared with a plain design.
- What is a half‑drop match?
- In a half‑drop, the motif on every second drop is offset by half the repeat. This may require additional length for alternate drops to maintain alignment.
- How accurate is the across‑width rounding?
- Across‑width rounding is an industry‑style approximation that assumes edge alignment to the next repeat. Real projects can vary depending on installer technique and tolerance for trimmed motifs.
- Should I add an extra allowance even for plain carpets?
- Yes. Site conditions, squareness, and cutting loss make an extra allowance prudent even without a repeat. The input lets you choose a value to match your risk tolerance.
- Can this tool handle multiple rooms or stairs?
- The model is for single rectangular spaces. For multi‑room layouts or stairs, run each area separately or use a specialized estimator.
- What roll width should I choose?
- Use the actual width supplied by the product line. Trying both common widths helps you see how drops and waste shift with different goods.
Tips
- Try both straight and half‑drop to see match impact.
- Experiment with 12 vs 15 ft (or 4 vs 5 m) roll widths.
- Use the cost input to visualize budget differences.
- Export results to discuss with your installer or client.
Example data table (static)
| Scenario | Design | Drops | Total cut length | Area used | Waste % |
|---|---|---|---|---|---|
| Plain baseline | Plain | — | — | — | — |
| Patterned straight | Patterned | — | — | — | — |
| Patterned half‑drop | Patterned | — | — | — | — |