Hip Roof Calculator
Calculate hip roof area, common rafter length, hip rafter length, ridge board length, jack rafter spacing, and a complete material takeoff — including pyramid roof detection.
Measure the outer walls of the building. For a hip roof, the length is the dimension parallel to the ridge board. Enter equal length and width for a pyramid (tent) roof.
Fill in Steps 1-3 and click Calculate to see your hip roof area, rafter lengths, ridge board, jack rafter list, and material takeoff.
| Framing Member | Count | Length Each | Total Linear Ft | Notes |
|---|
| Jack Rafter # | Position from Corner | Length | Notes |
|---|
| Material | Qty (exact) | Qty (order) | Unit |
|---|
Framing Tip: Hip rafters carry concentrated loads from all the jack rafters framing into them, so they are typically cut from deeper or wider stock than common rafters. Consult your structural engineer or building inspector before specifying hip rafter lumber size for any load-bearing application.
Hip Roof Calculator: How to Measure and Calculate a Hip Roof
A hip roof calculator computes the unique geometry of a four-sided roof where all four planes slope upward to a central ridge (or peak), rather than a gable roof where two planes slope to a ridge and the remaining two sides are vertical triangular end walls. Hip roofs are considerably more complex to calculate and frame than gable roofs because they introduce two additional rafter types — hip rafters and jack rafters — that each require their own length formulas and compound miter cuts.
This advanced calculator handles the full geometry: common rafter length, hip rafter length, ridge board length, jack rafter lengths at each spacing position, total sloped roof area, and material quantities. Enter your hip roof measurements — building outer wall dimensions, desired pitch (this hip roof pitch calculator supports 3/12 through 12/12), overhang, and rafter spacing, and the calculator derives every dimension you need to frame or estimate your hip roof.
Quick Reference: For a 40 x 28 ft building at 6/12 pitch with 12-inch overhangs, a hip roof has a ridge board of about 12 ft, common rafters of about 9.4 ft, hip rafters of about 13.3 ft, and a total sloped area of roughly 1,460 sq ft (14.6 roofing squares). Hip roofs use 10-15% more framing lumber than equivalent gable roofs due to the four hip rafters and their associated jack rafters.
Hip Roof vs Gable Roof: When to Use Each
Understanding the fundamental difference between a hip roof and a gable roof helps explain why the hip roof calculator needs to compute so many more values than a basic gable roof calculator. In a gable roof, two sloped planes meet at a central ridge, and the two end walls are vertical triangular “gables” that require no roof framing — just wall framing. In a hip roof, all four sides slope upward, eliminating vertical gable end walls and replacing them with two additional triangular sloped planes framed with hip rafters and jack rafters.
Hip Roof Advantages
The hip roof angle calculator in the results above gives you both the common rafter angle and the shallower hip rafter angle for your selected pitch. Hip roofs are the preferred choice in regions with high winds, hurricanes, or severe thunderstorm exposure, because all four sloped sides shed wind pressure more evenly than a gable roof’s vertical end walls, which act as sails in high-wind events. FEMA studies of hurricane damage in Florida and along the Gulf Coast have consistently found that hip-roofed homes sustain less wind damage than equivalent gable-roofed homes, even when both use the same roofing material and fastener schedules. Many coastal and southern building codes now incentivize or require hip roofs or reinforced gable construction for new residential buildings in high-wind zones.
Hip Rafter Calculator: Understanding the Diagonal Run
The defining geometric feature that any hip rafter calculator or hip rafter length calculator must handle is that the hip rafter does not run perpendicular to the ridge like a common rafter — it runs diagonally from each corner of the building to the end of the ridge board at a 45-degree angle (in plan view). This diagonal path means the horizontal run of a hip rafter is the half-span of the building multiplied by the square root of 2 (approximately 1.414), since the diagonal of a square with sides equal to the common rafter run is always that run times the square root of 2.
Hip Roof Ridge Length Calculator
The hip roof ridge length calculator formula is simpler than most homeowners expect: for a regular hip roof where all four sides have the same pitch, the ridge board length equals the building length minus the building width. This is because the two triangular hip end sections each consume exactly half the building width (one run on each end) of the total roof length before the ridge begins. For a 40 x 28 ft building, the ridge is 40 – 28 = 12 ft. When length equals width, the ridge length is zero and the roof becomes a pyramid.
Jack Rafter Calculator: The Decrement System
Jack rafters are the shorter rafters that fill the triangular sections between each hip rafter and the ridge. They run parallel to common rafters but decrease in length by a fixed increment as they step closer to the corner of the building. Using a jack rafter calculator, this decrement equals the rafter spacing multiplied by the pitch factor (the same pitch factor used to find common rafter length from run). Every successive jack rafter, moving one spacing interval closer to the corner, is shorter by exactly this decrement.
Hip Roof Area Calculator: Four-Plane Geometry
Calculating hip roof area with a hip roof area calculator requires accounting for all four sloped planes: two trapezoidal planes (the long sides) and two triangular planes (the hip ends). The most reliable approach for this hip roof square footage calculator is to compute the total area using the footprint method: multiply the effective footprint area (including overhangs) by the pitch factor. This works because the pitch factor converts horizontal plan area into sloped surface area regardless of how many planes the roof has, as long as all planes share the same pitch — which is the standard assumption for a regular hip roof.
Pyramid Roof Calculator: The Special Case
When a building’s length equals its width, the ridge board length drops to zero and the four hip planes meet at a single central peak instead of a ridge. This creates what is commonly called a pyramid roof, hip roof tent, or pavilion roof. The pyramid roof calculator mode in this tool detects this automatically when you enter equal length and width values and adjusts the outputs accordingly: the ridge length shows zero, the framing table omits the ridge board, and all four rafter sets become identical triangular planes. Pyramid roofs are common on residential additions, gazebos, and bay window projections.
Hip Roof Framing Calculator: Complete Step-by-Step
A full hip roof framing calculator workflow proceeds in this order: set the ridge board first (supported by temporary posts or a structural beam), install the four hip rafters at each corner diagonally to the ridge ends, then install the common rafters along both long sides, and finally fill in the triangular end sections with jack rafters spaced at your chosen on-center spacing. Each successive jack rafter is cut shorter by the decrement value, so a set of four jacks at 24-inch spacing will each be shorter than the previous by the same fixed amount.
| Pitch | Common Pitch Factor | Hip & Valley Factor | Hip Rafter Angle |
|---|---|---|---|
| 3/12 | 1.031 | 1.436 | 14.0° |
| 4/12 | 1.054 | 1.453 | 18.4° |
| 5/12 | 1.083 | 1.474 | 22.6° |
| 6/12 | 1.118 | 1.500 | 26.6° |
| 7/12 | 1.158 | 1.530 | 30.3° |
| 8/12 | 1.202 | 1.564 | 33.7° |
| 9/12 | 1.250 | 1.601 | 36.9° |
| 10/12 | 1.302 | 1.642 | 39.8° |
| 12/12 | 1.414 | 1.732 | 45.0° |
Related Roofing Calculators & City Guides
Frequently Asked Questions
How do I calculate hip roof area?
What is a hip rafter and how is its length calculated?
How do I calculate ridge board length for a hip roof?
What is the hip and valley factor?
What are jack rafters and how long should they be?
How is a hip roof different from a gable roof for framing purposes?
Why is the hip rafter angle shallower than the common rafter angle?
What is a pyramid roof?
Are hip roofs better for high-wind areas?
How many more shingles does a hip roof need than a gable roof?
Sources & Data
- National Roofing Contractors Association (NRCA) – Roofing Manual, 2026 Edition
- American Wood Council (AWC) – Span Tables for Joists and Rafters, 2026
- FEMA – Home Builder’s Guide to Coastal Construction, Hurricane Wind Resistance