Hip Roof Calculator
Last reviewed How we calculate
A hip roof slopes down on all four sides, so instead of two gable walls it has four hips running from the corners up to a short ridge. This works out the roof area and the length of every edge from the building size and the pitch.
Hip roof area, ridge and hips
Roof area, ridge length and hip lengths for a hip roof, from the building size and pitch.
How to measure
This calculator needs JavaScript to work. The measurements below are the ones you would need to do the sum by hand.
Roof area All four faces, at one pitch.
- Squares to order, with waste
- Ridge length
- Length of each hip
- All four hips
- Ridge and hips together What the ridge cap has to cover.
- Eaves perimeter For drip edge, starter and gutters.
- Height of the ridge above the eaves
The two sides are equal, so this is a pyramid hip: four hips meet at a point and there is no ridge.
This assumes a plain rectangle with all four faces at one pitch. At one pitch a hip roof has the same surface area as a gable on the same footprint; what changes is the edges. Hips need cap shingles and cut courses on both sides, which is why hip roofs take more waste than gables.
How the calculation works
When all four faces share one pitch, the roof area is simply the footprint times the pitch multiplier, exactly as it is for a gable. The ridge is the length of the building less its width, because each end loses half the width to the hip faces. Each hip runs diagonally from a corner, covering half the width in each direction on plan, and climbs the height of the ridge on the way.
A worked example
A building 40 ft by 28 ft, measured to the drip line, with a 6 in 12 roof, has a roof area of about 1,252 sq ft, or 13.77 squares once 10 percent waste is added. The ridge is 12 ft long and sits 7 ft above the eaves. Each hip is 21 ft, so the four together are 84 ft, and the ridge cap has to cover 96 ft in all. The eaves perimeter is 136 ft.
Why hip roofs need more waste
A hip roof has the same area as a gable of the same pitch, but every course on the hip faces is cut to an angle where it meets the hip, and the offcuts are usually too small to use. That is why 15 percent waste is common on hip roofs where 10 percent would do on a plain gable. When the building is square, the ridge disappears and the four hips meet at a point, which is called a pyramid hip.
Where this method is wrong
It assumes a plain rectangle with one pitch all round. An L-shaped hip roof, a wing at a different pitch or a dormer each need working out separately; the multi-section roof area calculator adds them up.
Frequently asked questions
Does a hip roof have more area than a gable roof?
Not at the same pitch on the same footprint: the roof area is the footprint times the pitch multiplier in both cases. A hip roof has more edges, though, so it takes more cap shingles and more waste.
How long is a hip on a hip roof?
Each hip runs from a corner to the ridge. Its length is the square root of twice the half-width squared plus the ridge height squared, which the calculator works out for you.
How much ridge cap does a hip roof need?
Enough for the ridge plus all four hips. The calculator adds them together as the length the cap shingles have to cover.