Category: Construction Calculators

Hip Roof Calculator: Area, Slope, Volume, Ridge, Hips & More

by
Jack Gray is an independent commercial roof consultant with over 25 years of experience in the roofing industry. He's trying to make the roofing information you find on the internet better, one article at a time.
A Ghiblified picture of a house with a hip roof.
A house with a regular hip roof (and no door, for some reason, must be around the back)

What Is a Hip Roof?

A hip roof is a type of roof where all sides slope downward from a central ridge (or apex, for a pyramid hip roof) with no vertical gable ends. It typically has four sloping faces: two trapezoidal sides that meet at the ridge, and two triangular ends called hip ends. The eaves are continuous around all four sides of the structure.

Hip roofs are known for their resistance to wind uplift, making them a popular choice in hurricane-prone regions. Structurally, the inward slope on all sides adds strength and rigidity, distributing loads more evenly across the walls below. Hip roofs are commonly found on residential structures, especially in areas requiring more sturdy roof profiles. When the footprint is square and the ridge disappears entirely, the result is a pyramid hip roof.

What This Calculator Does

This hip roof calculator helps you determine the important dimensional attributes of a hip roof based on your input values:

  • Total roof surface area: sum of the two longer trapezoidal roof surfaces and the two triangular hip ends.
  • Footprint area: building width × length.
  • Attic volume: an estimate of the enclosed space under the roof. Read more about hip roof attic volume.
  • Perimeter: total roof edge length.
  • Ridge length: difference between building length and width.
  • Roof height: from eave to ridge, either directly input or calculated from slope.
  • Slant height: hypotenuse from eave to ridge.
  • Pitch (rise/run) and degrees: both expressions are shown.
  • Pitch multiplier: slant height ÷ horizontal run (used for material estimating). Read more about roof pitch multipliers.
  • Hip rafter length: hypotenuse from eave corner to ridge end.
  • Total hip length: sum of all four hips.
  • Hip rafter slope: both in degrees and “X in 12” format. Read more about hip rafter slope.

How to Use It

  1. Choose your measurement system: Select USA (feet and X-in-12 roof pitch) or Metric (meters and degrees). The calculator accepts decimal values.
  2. Select input mode:
    • Use a Height Input if you know the vertical rise of the roof from eave level to ridge level.
    • Use a Slope Input if you know the roof slope (e.g. 6 in 12 or 30°).
  3. Enter the roof’s base width and base length:
    • Width = shorter side of the building (typically front to back)
    • Length = longer side of the building (typically left to right)
    • Tip: Length must be greater than or equal to width, otherwise the calculator will show an error.
  4. Enter the roof height or the slope, depending on which mode you selected.
  5. Click Calculate to see the results.
  6. Use the Clear button to reset the inputs and results.

Important Notes

  • In Slope Mode, the calculator automatically determines the roof height based on the slope and width inputs. In Height Mode, the slope is calculated from the width and height inputs.
  • In USA Mode, enter just the first number of the slope ratio. For example, input 6 for a 6-in-12 roof. Decimal slopes (like 7.5) can be entered.
  • All inputs must be positive decimal numbers. Do not use fractions, inches, or millimeters. Use decimals only (10.25 feet).
  • The roof width must not exceed the roof length. The calculator will return an error if the width is greater than the length, which would result in an invalid ridge length.
  • The ridge length is calculated by subtracting the width from the length. A ridge length of zero indicates a pyramid-style hip roof.
  • The roof pitch multiplier is calculated from the slope and used to convert the roof footprint area into the sloped roof surface area.
  • All calculations are based on a regular hip roof with two trapezoidal slopes and two triangular hip ends. Irregular or complex hip roof shapes are not supported.

Hip Roof Calculator

This is not a framing calculator. Note that in order to facilitate proper rafter layout, the real ridge length of a hip roof will actually be the roof length minus the roof width PLUS the thickness of the ridgeboard, so typically (theoretical ridge) +1.5 inches.

Don’t forget to include any eave overhang in your roof dimension inputs; roofs typically extend farther out than the exterior walls of the building, so you can’t just use the width and length of the walls.

Hip Roof Calculator

Results:

Total Roof Surface Area:
Roof Footprint Area:
Hip Roof Attic Volume:
Roof Edge Perimeter:
Ridge Length:
Roof Vertical Rise (Height):
Roof Surface Slant Height (Eave to Ridge):
Roof Slope:
Roof Pitch Multiplier:
Area of One Trapezoidal Side:
Area of One Hip End:
Hip Rafter Length:
Combined Length of All Hips:
Hip Rafter Slope:
Author Image

About the Author

Jack Gray spent 20 years as a principal roof consultant with the Moriarty Corporation, an award-winning building enclosure consultant firm founded in 1967. Mr. Gray has worked in the roofing industry for over 25 years, with training and practical experience in roof installation, roof inspection, roof safety, roof condition assessment, construction estimating, roof design & specification, quality assurance, roof maintenance & repair, and roof asset management. He was awarded the Registered Roof Observer (RRO) professional credential in 2009. He also served as an infantry paratrooper in the 82nd Airborne Division and has a B.A. from Cornell University.