Gable Siding Calculator
Work out the triangular gable area under your roof and roll it into your siding total — the part most estimates miss.
Walls (feet)
Gables / triangles optional
Windows & doors to subtract
Tip: measure each wall's width × height at its widest points. A per-wall audit table appears below so you can check every number.
Your siding squares, panels and cost appear here.
Estimated from wall count and perimeter — confirm against your actual corners and openings.
Cost per sq ft: – · per square: –
| Surface | Area (sq ft) |
|---|
The triangle everyone forgets
Gable ends are the triangular wall sections beneath a pitched roof, and they're the single most commonly forgotten surface in a siding estimate. Because they're up high and oddly shaped, people either skip them or guess. The math is easy, though: a gable's area is half its base times its height to the peak. Two identical gables? Double it. This calculator handles as many as your roofline has.
Enter each gable's base and rise, add your main walls, and the tool combines them into total area, squares and material. Gables often push waste higher because of the angled cuts along the rake, so consider bumping your allowance.
Step-by-step: from tape measure to order
The whole process is measure, subtract, pad, convert. Here's how that maps onto the fields above.
- Set your basics. Units and material at the top control everything downstream, so start there.
- Walls, one at a time. Enter width × height × quantity for each face of the house.
- Triangles and cut-outs. Add gable base and rise; subtract every significant window and door.
- Cushion and cost. Choose a waste percentage and, if you're budgeting, set labor and removal rates.
- Review the breakdown. Check the per-wall audit, then print or share.
Gable area math
A gable 28 ft wide at the base and 9 ft to the peak: ½ × 28 × 9 = 126 sq ft. A house with two matching gables has 252 sq ft of gable wall — over 2.5 squares that a rectangle-only estimate would miss entirely.
About the accuracy of these results
We'd rather be transparent than falsely precise. The quantity math is deterministic and matches standard takeoff practice, so if your inputs are right, your squares and piece counts are right. Where real-world variation lives — coverage by profile, and installed cost by region and crew — we use typical published figures and present them as ranges. That makes this a strong planning number, not a binding quote; a contractor's field measure remains the final word.
Gables, dormers and the tricky bits above the wall
Gable triangles are the start; roofs throw a few more shapes at you. Here's how to handle the ones that trip people up.
- Dormers: each dormer face is a small gable — measure its base and rise and add it like any other triangle.
- Unequal (saltbox) gables: if the peak isn't centered, the area is still ½ × base × height; the off-center peak doesn't change it.
- Steep pitches: a tall rise means more area and more angled rake cuts, so raise your waste allowance.
- Gable vents: subtract a large gable vent the way you'd subtract a window if it's sizable.
Add every triangle above — gables and dormers alike — and the tool folds them into your total so the high, easy-to-miss area is never left out.
Frequently asked questions
How do I calculate gable siding?
How do I measure a gable end?
Do gables increase how much siding I need?
Should I add extra waste for gables?
Notes from the field
"Added both gables and my order jumped by three squares — exactly what I'd have been short."