Gable roof: what it is, its parts, and how to measure one
A gable roof is two sloped planes meeting at a ridge, with a triangular wall, the gable, at each end. To measure one, find each plane's slope length (half the width plus the overhang, times the pitch's slope factor) and multiply by the ridge length, then double it. A 40 by 30 foot house with 1 foot overhangs at 6:12 has about 1,503 square feet of roof, 15 squares before waste.
Anthony Hicks30+ years in construction. Updated November 5, 2026.
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What a gable roof is
A gable roof has two slopes that meet along a ridge at the top. At each end, the wall rises to a point under the roof: that triangle is the gable. The sloped edges over the gables are the rakes; the level edges along the bottom are the eaves. The roof types guide compares it with hip, gambrel, mansard and other shapes, and the guide to the rake shows each edge.
Gable or hip
| Gable roof | Hip roof | |
|---|---|---|
| Slopes | Two | Four |
| Ends | Gable walls under the rakes | Sloped hip ends, no gable walls |
| Edges | Eaves on two sides, rakes at the ends | Eaves all the way around, hips at the corners |
| Ridge | The full length of the roof | Shorter than the roof by its width, at one pitch all around |
| Area, same house and pitch | The same as a hip roof | The same as a gable roof |
Over the same footprint at the same pitch, a gable roof and a hip roof have the same roof area, because each is the footprint tipped up by the pitch. The difference is in the edges: a gable roof has rakes and gable walls to side, a hip roof has hips to cap and more eave to gutter. The hip roof guide works one out.
How to measure a gable roof
- Measure the roof’s footprint, overhangs included: the length along the ridge and the width across it.
- Find the slope factor for the pitch: 1.054 for 4:12, 1.118 for 6:12, 1.202 for 8:12. The roof pitch guide gives others.
- Slope length of one side = half the width × the slope factor.
- Area of one side = slope length × the length. Double it for both sides.
- Squares = the area ÷ 100, then add waste for cutting.
A worked example
A 40 by 30 foot house with 1 foot overhangs all around, at 6:12:
| Step | Working | Result |
|---|---|---|
| Footprint with overhangs | (40 + 2) × (30 + 2) | 42 by 32 ft |
| Slope length, one side | (32 ÷ 2) × 1.118 | 17.9 ft |
| Area, both sides | 17.9 × 42 × 2 | 1,503 sq ft |
| Squares | 1,503 ÷ 100 | 15.0 squares before waste |
| Ridge | The roof’s length | 42 ft |
| Eaves | Two sides × 42 | 84 ft |
| Rakes | Four × 17.9 | 72 ft |
Footprint × slope factor gives the same area in one step: 42 × 32 × 1.118 = 1,503. The roofing calculator does it for any size and pitch, with the shingles, underlayment, drip edge and ridge cap.
Common questions
What is the difference between a gable and a hip roof?
A gable roof has two slopes and a triangular wall at each end; a hip roof slopes on all four sides and has no gable walls.
Is a gable roof cheaper than a hip roof?
On the same house at the same pitch the roof area is the same, so the shingles are close. A hip roof has hips to cut and cap and eaves all the way around for gutters; a gable roof has rakes and gable walls to finish.
What is a cross gable roof?
Two gable roofs meeting at right angles, such as a wing off the main house, with a valley where they join. The guide to roof valleys covers the joint.
How do I measure a gable roof from the ground?
Measure the house’s length and width at the walls, add the overhangs, and find the pitch from a rake or from the attic. A satellite roof report or a measured sketch from a phone gives the same numbers without the ladder.