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Table of Contents
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: vertical distance from eave level to ridge level, calculated from width and 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 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.
- And more
How to Use It
- Choose your measurement system: Select USA (feet and X-in-12 roof pitch) or Metric (meters and degrees). The calculator accepts decimal values.
- Enter the slope of the roof: Enter the slope in standard pitch for USA mode. Enter the X for your X-in-12 roof pitch. For example, enter “6” for a 6-in-12 slope. Enter the slope in degrees in metric mode, i.e., enter “30” for a 30° roof slope. If you aren’t sure what the slope is, you could get yourself one of these pitch measurement tools (on Amazon). I have one and it works very well. I also made a roof pitch visualizer tool you can use to help you make an educated guess.
- Enter the width and length of the building:
- Width = shorter side of the building (typically front to back) measured to the outsides of the exterior walls
- Length = longer side of the building (typically left to right) measured to the outsides of the exterior walls
- Tip: Length must be greater than or equal to width, otherwise the calculator will show an error.
- Enter roof eave overhang:
- The eave overhang is the extension of the roof beyond the outside surfaces of the building’s exterior walls (entered as inches or millimeters). Because of a hip roof’s typically symmetrical geometry, this single input is applied equally to all sides. You can set it to 0 if the roof has no overhang.
- You are entering the horizontal width of the eave overhangs, not the sloped surface (the calculator figures that out). You should be able to figure this out by standing under the eave and looking up, and measuring the distance from the outside edge to the wall.
- Click Calculate to see the results.
- Use the Clear button to reset the inputs and results.
Important Notes
- In USA Mode, enter just the first number of the slope ratio. For example, input 6 for a 6-in-12 roof. Slopes with decimal fractions (like 7.25) can be entered.
- All inputs must be positive decimal numbers. Do not use regular fractions. Use decimals only (i.e., 10 feet 3 inches should be entered as 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, when using 2-by-X rafters and ridge board, 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 the ridge length will be the theoretical ridge length +1.5 inches. This is so the ridgeboard can fully catch the rafters at the very end of the ridge while maintaining the proper rafter layout; without the extra 0.75″ at each end of the ridge, the ridge would only catch half the width of those rafters.
If you are looking for expert guidance on framing a hip roof, I recommend you get a copy of A Roof Cutter’s Secrets to Framing the Custom Home (link is to Amazon).
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.