Enter either dimensions or total area, pick a panel size, then add waste and optional costs.
| Scenario | Input | Panel | Factors | Panels needed |
|---|---|---|---|---|
| Garden shed floor | 10 ft × 12 ft, 1 room, 0 openings | 4 × 8 ft | Waste 10%, Loss 0% | 5 |
| Tool room with door cutout | 4 m × 3 m, 1 room, 1.8 m² opening | 4 × 8 ft | Waste 12%, Loss 2% | 5 |
| Two identical bays | 8 ft × 14 ft, 2 rooms, 0 openings | 4 × 10 ft | Waste 8%, Loss 3% | 7 |
Examples are illustrative; your totals depend on panel size and waste.
Floor Area is computed from dimensions or entered directly, then openings are subtracted:
- Floor Area = (Length × Width) × Rooms
- Net Area = Floor Area − Openings
- Needed Area = Net Area × (1 + Waste%) × (1 + Loss%)
- Panels = ceil(Needed Area ÷ Panel Coverage)
The ceiling step rounds up to whole panels so you can actually buy them.
- Pick your units, then choose dimensions or total area.
- Enter room size, number of rooms, and any openings.
- Select a sheet size, or choose custom for special panels.
- Add waste and optional layout loss for realistic ordering.
- Optionally enter price, tax, and delivery to estimate totals.
- Press calculate, then download a CSV or PDF report.
For garden structures, double-check local span and rating requirements.
Panel yield planning for outdoor floors
Subfloor panels are typically sized to balance stiffness, handling, and seam count. A larger sheet reduces joints, but can increase offcut waste if the floor has many projections. Use this calculator to compare 4×8, 4×9, and 4×10 sheets against your net floor area.
Waste factor ranges you can justify
For rectangular garden sheds and simple storage rooms, 8–12% waste usually covers perimeter trims and minor defects. For angled walls, multiple door cutouts, or frequent penetrations, 12–18% is more realistic. Keeping waste explicit helps you explain purchasing decisions and prevents last-minute shortages.
Layout loss and seam strategy
Layout loss is a separate buffer for planning seams over joists, staggering panel joints, and trimming tongue-and-groove edges. A 0–5% layout loss often covers these practical adjustments. When you rotate sheets to align seams, you may gain strength but lose some usable coverage to trimming. If your build requires blocked seams or extra nailing, keep a small loss factor so the order remains accurate.
Comparing sheet sizes with quick math
Panel coverage is simply width × length. A 4×8 sheet covers 32 sq ft, a 4×9 covers 36 sq ft, and a 4×10 covers 40 sq ft. After subtracting openings, the calculator multiplies net area by waste and layout loss, then rounds up to whole panels. This produces an orderable count and an overage for contingency. If you work in metric, the calculator converts square meters to square feet so inputs stay consistent.
Cost checks that match real purchasing
Enter a per-panel price to estimate subtotal, then add tax and delivery for a total spend view. This is useful when comparing thickness options, as thicker panels can reduce deflection over longer spans. Use the overage value to decide whether to keep one spare sheet on-site for repairs, future shelving, or patching. Exporting a CSV or PDF keeps a record you can share with suppliers or your build crew, and it makes reorders faster if your project scope changes.
1) Should I subtract door openings from the floor area?
Only subtract areas you will not sheet at all. For most shed floors, doors sit on top of the subfloor, so you usually do not subtract the doorway unless you are leaving a true void.
2) What waste factor should I use for a simple rectangle?
Start with 10%. Increase if panels must be ripped narrow, the floor is out of square, or you expect defects. Reduce only if you have a proven cut plan and consistent dimensions.
3) When is layout loss different from waste?
Waste covers offcuts and mistakes. Layout loss covers strategic seam placement and trimming for fit. Using both lets you separate cutting inefficiency from structural layout decisions.
4) Does the calculator account for panel orientation?
It estimates by area, not a cutting diagram. Orientation can change how many full sheets you can use. If you are near a threshold, add a small layout loss or test another sheet size.
5) Why does it round up to whole panels?
Panels are purchased as whole sheets, and offcuts are not guaranteed to fit future pieces. Rounding up ensures you have enough coverage after waste and trimming.
6) How can I reduce the panel count safely?
First, reduce waste only if you can simplify cuts and limit openings. Next, compare a larger sheet size if handling is feasible. Avoid lowering thickness or seam support without checking span ratings and local requirements.