Hip Roof Calculator
A hip roof slopes down to the walls on all four sides, with no vertical gable ends. Enter the building's footprint and pitch below and the calculator returns the roof area, the roofing squares, and the two numbers a hip roof needs that a gable does not: the ridge length and the hip rafter length.
What is a hip roof?
A hip roof has four sloping planes instead of two. On a rectangular building the two long sides are trapezoids, the two ends are triangles, and they meet along a ridge that is shorter than the building. The sloping line where two planes meet at a corner is the hip, which is where the roof gets its name.
A gable roof, by contrast, has two planes and two vertical triangular walls at the ends. Those end walls are the gables, and they are wall area rather than roof area, which the wall square footage calculator handles.
A pyramid hip is the special case where the building is square. The ridge shrinks to nothing and all four planes meet at a single point.
The surprise: a hip roof covers the same area as a gable
This is the thing most roofing content gets wrong, and it is worth stating plainly.
A hip roof and a gable roof on the same footprint, at the same pitch, have exactly the same surface area.
The reason is straightforward once you see it. Look at a hip roof from directly above. The four planes carve the rectangle into two trapezoids and two triangles, and those four plan areas add up to precisely the footprint, no more and no less. Every plane sits at the same pitch, so every one of them is stretched by the same pitch factor. Total surface area is therefore footprint times pitch factor, which is exactly the gable formula.
Roof area = footprint × pitch factor
Take a 40 by 30 foot building at a 6/12 pitch, the same example used on the roof square footage calculator. The pitch factor is 1.118.
- Gable: 1,200 × 1.118 = 1,341.6 sq ft
- Hip: the two trapezoids come to 750 sq ft in plan (each is ((40 + 10) ÷ 2) × 15 = 375), the two triangles to 450 (each is 30 × 15 ÷ 2 = 225), totalling 1,200, and 1,200 × 1.118 = 1,341.6 sq ft
Identical. So if you only need the area, the roof calculator already has you covered whichever shape you have.
Where a hip roof actually costs more
The extra cost is real, it just is not in the square footage. It is in three places.
1. Ridge and hip cap
This is the big one, and it is easy to quantify. A gable roof has one capped line: the ridge. A hip roof has a shorter ridge plus four hips, every one of which needs cap shingles.
On a regular hip roof with equal pitch all round:
Ridge length = building length − building width
Hip rafter length = √( 2 × (width ÷ 2)² + rise² ), where rise = (width ÷ 2) × (pitch ÷ 12)
For the 40 by 30 at 6/12: the ridge is 40 − 30 = 10 feet. Half the width is 15 feet, so the roof rises 15 × 0.5 = 7.5 feet to the ridge, and each hip rafter is √(2 × 15² + 7.5²) = √506.25 = 22.5 feet.
| Gable | Hip | |
|---|---|---|
| Ridge | 40 ft | 10 ft |
| Hips | none | 4 × 22.5 = 90 ft |
| Total cap | 40 ft | 100 ft |
Two and a half times the cap material, on a roof with identical square footage. Cap shingles are sold by the linear foot of coverage, so that difference goes straight onto the order.
2. Waste
Every hip means shingles cut on a bevel where a course runs into it, and the offcuts are rarely reusable. A plain gable wastes about 10 percent. A hip roof starts around 15 percent, and a hip roof with valleys or dormers on top of that runs higher still.
Same area, more cuts, more waste. The calculator above builds in 15 percent.
3. Labour and framing
Hip rafters are cut on compound angles and the jack rafters running into them all differ in length. It is slower work than a gable, both in framing and in shingling, which is why a hip roof quote comes in higher even when the material count looks similar.
Hip roof vs gable roof
| Hip roof | Gable roof | |
|---|---|---|
| Planes | Four | Two |
| End walls | None, roof slopes all round | Two vertical gable walls |
| Surface area | Same for the same footprint and pitch | Same |
| Ridge and hip cap | Much longer | Ridge only |
| Waste factor | 15 percent and up | About 10 percent |
| Wind performance | Better, no flat end wall to catch wind | The gable end is the weak face |
| Attic space and ventilation | Less of both | More of both |
| Cost | Higher | Lower |
The wind point is the main reason hip roofs dominate in hurricane-prone regions. There is no large vertical end wall for wind to push against, and the four-way slope braces itself.
The trade is attic volume. A gable gives you a full-height space the length of the house; a hip roof cuts the ends off it, which costs you storage and makes ridge ventilation trickier.
Other roof shapes
Hip and gable are the two that cover most houses, but the same footprint-times-pitch-factor logic applies to any roof made of flat planes.
| Shape | What it is | Area note |
|---|---|---|
| Gable | Two planes meeting at a ridge | Footprint × pitch factor |
| Hip | Four planes, no gable ends | Footprint × pitch factor, same as gable |
| Pyramid hip | Square building, four planes to a point | Footprint × pitch factor |
| Shed | One single sloping plane | Footprint × pitch factor |
| Flat | No meaningful slope | Footprint × 1.0 |
| Gambrel | Two pitches per side, shallow over steep | Calculate each pitch band separately and add |
| Mansard | Four sides, each with a steep lower and shallow upper slope | Calculate each band separately and add |
Gambrel and mansard roofs are the exceptions that need more work, because a single pitch factor cannot describe them. Split the roof into its pitch bands, work out each band's plan area, apply that band's own pitch factor, and add the results. The how to calculate square footage guide covers the same break-it-into-pieces approach for any awkward shape.
Worked example: a 40 by 30 hip roof at 6/12
- Footprint: 40 × 30 = 1,200 sq ft.
- Pitch factor for 6/12: 1.118. The roof pitch calculator covers measuring the pitch and converting it to degrees.
- Roof area: 1,200 × 1.118 = 1,341.6 sq ft.
- Add 15 percent waste: 1,341.6 × 1.15 = 1,542.8 sq ft.
- Squares: 1,542.8 ÷ 100 = 15.4, round up to 16 squares.
- Bundles: 16 × 3 = 48 bundles of standard shingles.
- Ridge: 40 − 30 = 10 ft. Hips: 4 × 22.5 = 90 ft. Cap total 100 ft.
Compare that to the same house with a gable roof: identical 1,341.6 sq ft, but 10 percent waste instead of 15 gives 15 squares rather than 16, and 40 feet of cap instead of 100.
How to measure a hip roof from the ground
You do not need to get on the roof for a simple hip.
- Walk the perimeter and measure the building's outside length and width, including the eave overhang on all four sides. The overhang counts, and on a hip roof it counts on every side rather than just two.
- Get the pitch by holding a level against a rake edge, or by measuring rise against a foot of run on a rafter in the attic.
- Multiply footprint by the pitch factor.
- Measure the ridge if you can see it, as a check. It should equal length minus width on a regular hip. If it does not, the roof is not a regular hip and you will need to break it into pieces.
That last check is worth doing. Plenty of real roofs are hip-and-valley hybrids, with wings and dormers, and the clean formula stops applying the moment the plan is not a simple rectangle. When that happens, split the roof into rectangles, treat each one separately, and add the results.
Frequently asked questions
What is a hip roof?
A hip roof slopes down to the walls on all four sides, with no vertical gable ends. On a rectangular building the two long sides are trapezoids and the two ends are triangles, meeting along a ridge that is shorter than the building itself. The sloping corner line where two planes meet is called the hip.
Does a hip roof have more square footage than a gable roof?
No. On the same footprint at the same pitch the two have exactly the same surface area, because the four hip planes divide the footprint between them with nothing left over. A 40 by 30 building at 6/12 gives 1,341.6 square feet either way. The extra cost of a hip roof is in ridge and hip cap, waste and labour, not area.
How do I calculate the square footage of a hip roof?
Multiply the building footprint, including the eave overhang on all four sides, by the pitch factor for your roof slope. A 40 by 30 footprint at 6/12 is 1,200 × 1.118 = about 1,342 square feet. Add 15 percent for waste before ordering, since hips create more cut-offs than a gable.
How do I find the ridge length on a hip roof?
On a regular hip roof with equal pitch all round, the ridge is the building length minus the building width. A 40 by 30 building has a 10 foot ridge. If the building is square, the ridge disappears entirely and you have a pyramid hip.
How long is a hip rafter?
Take half the building width, square it, double that, add the square of the ridge rise, and take the square root. On a 40 by 30 at 6/12, half the width is 15 feet and the rise is 7.5 feet, so the hip rafter is the square root of (2 × 225 + 56.25), which is 22.5 feet.
How much more cap does a hip roof need?
A lot. A 40 by 30 gable has 40 feet of ridge to cap. The same building with a hip roof has a 10 foot ridge plus four 22.5 foot hips, which is 100 feet in total. That is two and a half times the cap shingles for the same roof area.
What waste factor should I use on a hip roof?
Start at 15 percent. Every hip means shingles cut on a bevel, and those offcuts rarely go back on the roof. A plain gable gets away with 10 percent. Add more still if the roof also has valleys, dormers or skylights.
Is a hip roof better than a gable in high wind?
Generally yes, which is why hip roofs are common in hurricane regions. A hip roof has no large vertical end wall for wind to push against, and the four-way slope braces itself. The trade-off is less attic volume and more awkward ridge ventilation.
For any other roof shape or a whole project at once, start from the roof square footage calculator or the homepage.
Related tools
Roof square footage calculator | Roof pitch calculator | Triangle calculator | Wall calculator