Inputs
Choose a preset to auto-fill roll size and typical laps.
ft
ft
in
Used for horizontal courses.
in
Used for vertical drops.
%
Includes cuts, trims, penetrations, handling.
ft²
Total area of windows/doors to exclude.
Corner-wrap allowance
Adds area for wrapping beyond outside corners. Uses average wall height.
in
Typical 6–12 in (150–300 mm).
Walls
| # | Length (ft) | Height (ft) | Action |
|---|
Results
Enter dimensions and press Calculate.
Common Roll Sizes
| Width | Length | Coverage (no laps) |
|---|---|---|
| 9 ft | 150 ft | 1350 ft² |
| 10 ft | 150 ft | 1500 ft² |
| 3 ft | 165 ft | 495 ft² |
| 1.5 m | 50 m | 75 m² |
| 3.0 m | 50 m | 150 m² |
Actual usable coverage reduces with laps, trims, corners, and waste.
Formulas Used
Net wall area Anet = Σ(L × H) − Aopenings
Average wall height H̄ = Σ(L × H) / Σ(L)
Corner-wrap allowance Acorner = Nc × wcorner × H̄ × f, where f is 1 for single-direction, 2 for both directions.
Effective roll width (horizontal courses): Weff = W − lapH
Effective roll width (vertical drops): Weff = W − lapV
Effective area per roll: Aroll = Weff × Lroll
Pre-waste demand: Apre = Anet + Acorner
Adjusted demand: Aadj = Apre × (1 + waste%)
Roll count: Nrolls = ceil(Aadj / Aroll)
Seam tape length (horizontal): Σ(max(0, courses − 1) × wall length)
Seam tape length (vertical): Σ(max(0, drops − 1) × wall height)
These simplified production formulas provide planning estimates. Always verify against manufacturer instructions and local codes.
How to Use This Calculator
- Select units, orientation, and a brand preset or enter custom sizes.
- Add walls with their length and height. Use “Load example” to see presets.
- Set overlaps, waste allowance, openings area, and corner-wrap details.
- Click Calculate to compute rolls, coverage, and seam tape.
- Download a CSV or PDF of your inputs and results.
- Adjust inputs to compare different roll sizes or application methods.
FAQs
A common starting point is 4 in horizontal laps and 6 in vertical overlaps, but always follow the specific product instructions and local code requirements.
Both methods are used. Horizontal courses often simplify drainage layering; vertical drops can reduce seams on tall walls. Choose the method that matches instructions, climate, and detailing.
It estimates flat wall areas with user-entered waste and a separate corner-wrap allowance. Complex geometries and bump-outs may require additional material and should be considered in allowances.
Yes. Enter the total openings area to exclude. For a more granular approach, sum each opening’s width × height and add them together.
The calculator estimates seam tape length by seams. Fastener counts vary by product, exposure, and code; consult the installation guide for spacing and cap fastener requirements.
Choose a preset that matches your roll size and common laps. You can switch to Custom and override any field while keeping the rest as set.
It treats each outside corner identically using average wall height. For varying heights, raise the corner count or wrap width to approximate extra complexity.