Rolled Roofing Calculator
Calculate how many rolls of mineral-surface rolled roofing you need for a low-slope shed or porch roof, plus total cost.
How this calculator works
Rolled roofing comes in rolls sized to cover 1 roofing square (100 sq ft) each. This calculator divides your roof’s surface area by 100 sq ft per roll, then rounds up to a whole roll since partial rolls aren’t sold.
Formula: Rolls = Roof area (sq ft) ÷ 100 sq ft per roll, rounded up.
Worked example
A 30 ft × 20 ft shed roof section (600 sq ft):
- Area: 30 × 20 = 600 sq ft
- Rolls: 600 ÷ 100 = 6.0 rolls
- At $50/roll, that’s $300.00 before waste.
- With 10% waste added: 6 × 1.1 = 6.6 → rounds up to 7 rolls, or $350.00.
Coverage reference
| Roof area | Rolls needed |
|---|---|
| 150 sq ft | 2 rolls |
| 600 sq ft | 6 rolls |
| 2,400 sq ft | 24 rolls |
How to measure your roof
Measure the length and width of the low-slope roof section you’re covering — sheds, porch roofs, and small additions are the typical use case here, not a full-pitch main roof. Add the required course overlap into your waste allowance, and check that your roof’s slope falls within the manufacturer’s minimum pitch rating before relying on rolled roofing alone.
Frequently asked questions
How much roof does one roll of rolled roofing cover?
A standard roll of mineral-surface rolled roofing covers 1 roofing square — 100 square feet. This calculator divides your roof area by 100 sq ft per roll and rounds up, since rolls are sold whole.
What kind of roof is rolled roofing meant for?
Rolled roofing is designed for low-slope roofs — generally under a 3:12 pitch — like sheds, porches, and small outbuilding roofs. It's not rated for steep-slope roofs where standard shingles or metal panels are the appropriate product.
Should I add waste to a rolled roofing order?
Yes — the 10% waste toggle accounts for the required overlap between courses (typically 2-4 inches) plus trimming at edges, hips, and any penetrations. Small roofs with lots of edges relative to their area often need a slightly higher allowance than the flat 10%.
Is rolled roofing nailed or glued down?
Both methods exist — exposed-nail application is faster and cheaper but leaves nail heads exposed to the weather at overlaps, while concealed-nail (or torch-down/adhesive) application hides the fasteners for better water resistance. Concealed methods cost more in labor and sometimes require a slightly higher roll count for the extra overlap needed.
How long does rolled roofing typically last?
5-10 years is a typical service life for standard mineral-surface rolled roofing, considerably shorter than shingles or metal, which is why it's usually reserved for lower-cost, lower-visibility structures rather than a primary residence's main roof.
Estimates only. Verify quantities with your supplier before purchasing.