Measure roof surfaces for gable, hip, shed, or flat designs today easily. Add pitch and overhangs, then export for bids and orders in minutes.
| Roof style | Length (ft) | Width (ft) | Overhang (ft) | Pitch | Waste | Roof area (ft²) | Squares |
|---|---|---|---|---|---|---|---|
| Gable | 40 | 28 | 1 | 6/12 | 10% | ~1,370 | ~13.7 |
| Shed | 30 | 18 | 0.5 | 4/12 | 8% | ~590 | ~5.9 |
| Flat | 25 | 20 | 0 | — | 5% | ~525 | ~5.3 |
Use this calculator to estimate roof coverage for planning and procurement. It converts pitch, overhangs, and waste into surface area, then translates area into squares, bundles, and roll quantities for clearer, consistent takeoffs.
Start with outside building dimensions and confirm the roof style. Add overhangs for eaves and rakes, then record units and assumptions. Consistent inputs make takeoffs repeatable across bids, change orders, and material reconciliations.
The plan footprint is the horizontal area. Roofing is installed on the sloped surface, so surface area rises with pitch. This calculator computes an expanded footprint first, then scales it to the surface area so ordering aligns with installed coverage.
Pitch is entered as rise/run, such as 6/12. The slope factor is √(1 + (rise/run)²). A 6/12 pitch produces about 1.118, meaning roughly 11.8% more surface than plan. Steeper roofs also increase fastening and staging needs.
Overhangs add real area and should not be guessed. Adding 1 ft on both sides increases each overall dimension by 2 ft. On a 40×28 footprint, that increases plan area by 136 ft² before pitch is applied, which can change bundle counts and delivery timing.
Waste covers trimming, starter strips, ridge caps, and offcuts. Use 5–10% for simple gables, 10–15% for hips and valleys, and higher for many penetrations or short runs. Applying waste after pitch better matches the installed surface you will actually cover.
Suppliers often quote in squares: 1 square equals 100 ft². If waste-included area is 1,370 ft², that is 13.7 squares. With 33.3 ft² per bundle, estimate about 42 bundles. Always verify the coverage printed on the product wrapper.
Underlayment is ordered by roll coverage, commonly 200–400 ft² depending on product. For 1,370 ft² and 400 ft² rolls, plan four rolls, plus extra for laps, valleys, and code-required ice protection. Exporting results helps keep accessory assumptions visible to stakeholders.
Dormers, multiple valleys, and curved sections should be field-measured by plane. Measure each plane along the slope, sum areas, then apply a conservative waste factor. When measurement is limited, choose a complex style option as a baseline and confirm before ordering.
Use outside dimensions for the roof footprint. If you only have inside dimensions, add wall thickness or confirm with drawings so you do not under‑order materials.
Use 5–10% for simple gables and long runs. Use 10–15% for hips and valleys. Increase further for many penetrations, short courses, or complex detailing.
Pitch increases surface area through the slope factor. A steeper pitch raises the factor, so the same plan footprint requires more roofing coverage and typically more labor.
Roofing squares are a common supplier unit defined as 100 ft². Bundles are usually labeled in ft² coverage. The calculator converts metric inputs to the same ordering units for consistency.
Yes for surface area and waste planning. Panel layouts depend on profile, laps, and rib spacing, so use the area result as a starting point and confirm with the manufacturer’s coverage tables.
Not explicitly. The waste factor is intended to cover typical starters, caps, and cutting losses. For detailed bids, itemize ridge length, hip length, and accessory quantities separately.
For accuracy, measure each plane and add them together. When you cannot, select “Complex” and use a higher waste factor, then validate with a full takeoff before purchasing.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.