Direct roof planes
Surface = Σ(plane length × slope length × quantity)
Slope length is already measured along the roof surface, so no pitch factor is added.
Roofing formulas
How roof surface and packages are calculated.
All lengths convert to canonical units first. Only the footprint method applies the selected pitch factor.
Footprint and pitch
Surface = projected area × √(1 + (rise ÷ 12)²)
The method assumes one rectangular projection and a uniform pitch. A 0:12 rise produces a factor of 1.
Order area
Order area = roof surface × (1 + allowance %)
The 10% starting allowance remains fully editable and never changes automatically.
Squares and packages
Squares = order ft² ÷ 100; packages = ceil(order area ÷ package coverage)
Roofing squares stay decimal; only verified whole packages are rounded up.
Measure and plan
Choose the method that matches your roof data.
Roof surface area
Use actual plane dimensions for complex roofs, or start with an actual sloped area from plans, an aerial report or a professional.
Roof pitch
A 6:12 pitch means 6 units of rise for every 12 units of horizontal run. The pitch factor converts horizontal projection to sloped surface.
Overhangs
Include overhangs in projected dimensions when they are part of the roofing coverage. The calculator does not infer them from building dimensions.
Roofing squares
A roofing square is the North American roofing term for 100 ft². It is an ordering expression derived from area, not a new physical unit.
Bundles and packages
Do not assume three bundles per square. Shingle exposure and packaging vary, so use the manufacturer coverage for the exact product.
Field roofing only
The result estimates field roofing coverage. Accessories and installation details require separate planning.
Before you order
What this roofing estimate includes
- Direct roof planes are modeled as rectangles measured along the actual slope.
- Footprint + pitch assumes a rectangular horizontal projection and one uniform pitch.
- Known roof area is treated as the actual sloped surface and receives no pitch adjustment.
- The 10% allowance is editable and never changes automatically for roof shape, pitch or product.
- Package estimates use only the manufacturer coverage entered for the exact roofing product.
- Material suitability, code compliance, structural design, labor, cost and tear-off are not included.
Use safe, reliable measurements
Do not access a roof if it cannot be measured safely. Plans, aerial measurements or a roofing professional can provide roof dimensions without unsafe roof access.
Starter courses, ridge/hip caps, flashing, underlayment and other roofing accessories are not included. Follow the roofing manufacturer’s installation instructions.
Roofing questions
Frequently asked questions
How many square feet are in a roofing square?
One roofing square equals 100 square feet. The calculator keeps this value decimal rather than rounding it to a whole square.
How do I calculate the square footage of a roof?
Measure actual rectangular roof planes and add their areas, or multiply a simple horizontal projection by the pitch factor. A known professional roof-area measurement can also be entered directly.
How does roof pitch affect roof area?
A steeper uniform pitch increases sloped surface above the horizontal projection. The footprint method uses √(1 + (rise ÷ 12)²).
How many bundles are in a roofing square?
There is no universal bundle count per square. Roofing products have different coverage, so use the manufacturer coverage per bundle or package.
How much extra roofing should I order?
Measivo starts at 10%. Complex roofs, valleys, hips and specific products may need more, so adjust it using manufacturer or installer guidance.
Should I include roof overhangs?
Yes when the overhangs are part of the surface being covered. Include them in your projected or direct plane dimensions rather than expecting the calculator to infer them.
Does this calculator include ridge cap and starter shingles?
No. Ridge and hip caps, starter courses, flashing, underlayment, membranes, drip edge, nails and ventilation are not included.
Can I measure my roof from the ground?
Plans, aerial reports and professional measurements can provide safer dimensions. Do not access a roof when it cannot be measured safely.
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Keep planning your project.
Use another Measivo calculator to estimate the next material on your list.