Gable Siding Calculator
Calculate gable siding for symmetric, offset-peak or shed ends. Find roof-pitch gable height, sloped rake trim lengths, whole trim sticks and siding packages.
Enter measurements below. The result updates as you type.
Calculation breakdown
Gable shape
Symmetric gable: two equal sloping rake runs; siding area = base × vertical rise ÷ 2.
Height source
Measured vertical height from eave/base to peak is used.
Net area
144 - 20 = 124 sq ft
Purchase quantity
124 sq ft plus 10% waste, divided by user-provided package coverage.
Rake trimming
13.416 + 13.416 ft sloped rake length per gable. Each sloped side independently rounds into full supplier stock lengths; no offcut sharing assumed. Shed gables have one sloped rake only.
Advertisement
More Siding help
Related calculators and guides
Open the project hub for nearby tools, measurement guidance, and published articles.
Formula explanation
Core gable siding estimate basis
Gable wall area = base width × vertical rise ÷ 2. For symmetrical pitch: rise = base width ÷ 2 × roof rise/run; for shed pitch: rise = base width × roof rise/run. For a measured offset peak, left rake = √(left run² + rise²), right rake = √((base − left run)² + rise²). Purchase siding area = (total wall area − total openings) × (1 + waste%). Whole rake trim pieces are rounded separately for each sloped edge.
- Measured-height mode uses the vertical gable height directly; an offset peak also needs its measured horizontal left run.
- Pitch mode is valid for symmetrical and shed shapes only, since a single pitch does not determine the two different slopes of an offset peak.
- The calculator uses vertical gable WALL area; roof covering and overhangs are excluded.
- One siding square equals 100 square feet.
Worked example
Two matching gables
Two 24 ft wide x 6 ft high gables, 20 sq ft openings, 10% waste
- 1Multiply 24 x 6 / 2 for one gable.
- 2Multiply by two matching gables.
- 3Subtract 20 square feet of openings.
- 4Apply the selected waste allowance and package coverage.
Purchase area: 136.4 square feet, or 1.36 siding squares before package rounding.
Estimate assumptions
Check these assumptions before ordering
- Each supported shape is a triangular wall: area equals horizontal base width times vertical rise divided by two, regardless of the peak location.
- A standard symmetrical gable has two equal sloped rakes; an offset-peak gable has unequal rake runs; a shed/half gable has one sloped rake and a vertical end.
- Symmetric pitch mode derives vertical rise from half the base width times rise/run; shed pitch mode uses the full base width. Offset-peak gables require a directly measured height.
- Openings are deducted before waste is applied.
- Only sloped rake trim is optionally counted, using real entered stock lengths rounded on each edge separately. Rake fascia, starter, soffit, flashing, and corner accessories are otherwise excluded.
- Supplier material prices are optional. Complete combined material and delivery quote requires both actual siding package and rake trim stick prices.
Measurement checklist
How to measure
- Measure the horizontal base width across the bottom of the gable.
- Measure vertical height from the base line to the peak, or use the applicable symmetrical or shed pitch mode. Do not enter roof-plane length as wall height.
- For an off-center ridge, measure horizontal distance from the left gable edge to the peak directly and use vertical-height mode.
- Count only truly matching gables with identical base, peak position, vertical height and material profile.
- Measure windows, doors and vents within all selected gables as a combined opening area. Do not subtract openings twice.
- If buying rake trim, use supplier stock lengths and manufacturer-compatible rake terminations before ordering.
Avoid these errors
Common mistakes
- Confusing sloped roof surface, rafter length or overhang with the triangular vertical gable wall area.
- Using half the base width to derive shed roof rise, although its single slope spans the full wall width.
- Forgetting that a triangular gable is half of a rectangle with the same base and height.
- Deducting openings after waste instead of before waste.
- Assuming an off-center peak has equal rake edge lengths or treating the vertical shed side as a sloped rake.
- Dividing total rake length by stock size without allowing each independently cut rake to require its own full-length pieces.
- Ordering gable siding without checking profile-specific coverage, flashing, starter and required rake trim joints.
Estimate disclaimer
Verify before ordering.
Use the output as a planning baseline. Site conditions, product coverage, waste, supplier units, installation method, and local requirements can change the final quantity.
Related calculators
Continue the same project estimate
Exterior Projects
Siding Calculator
Estimate siding for measured house walls, windows and gables; then turn square footage into actual supplier quantities. Use product-listed coverage or lap-plank length and installed exposed reveal, compare individual pieces with cartons and measure accessories separately.
Exterior Projects
Siding Square Calculator
Decode a contractor or supplier quote in siding trade squares (100 square feet each), or use known wall area. Convert to net square footage, optional waste, unopened product-specific cartons and leftover coverage; compare user-entered material rates per trade square versus full box without inventing market prices.
Exterior Projects
Vinyl Siding Calculator
Convert a measured single wall or previously measured gross siding area into vinyl panel and carton quantities. Cross-check actual panel reveal against printed box coverage, see where a full-course order differs from ideal square footage and enter real supplier prices instead of guessed costs.
Exterior Wall Materials
Stucco Calculator
Calculate base-coat and finish-coat purchases separately. Deduct measured openings, use coverage for the specified coat thickness, and round each product only after combining its required quantities.
Published guides
Understand the measurements and assumptions
Supporting guide
How Much Siding Do I Need?
Add wall and gable areas, subtract openings, convert to siding squares or product coverage units, and apply a clear waste allowance.
Read guide
Supporting guide
Vinyl Siding Cost by House Size: Area, Squares, and Scope
Learn why house floor area is not siding area, then estimate vinyl siding cost from measured walls, siding squares, product coverage, and project scope.
Read guide
Common questions
Use the result with context
01Does this replace the full siding calculator?+
No. This page is for triangular gable ends only. Use the full siding calculator for whole-house walls, multiple wall sections, and broader siding estimates.
02Can roof pitch be used instead of measuring gable height?+
Yes. Pitch mode derives gable height from half the base width multiplied by rise divided by run, but a measured height is usually better when available.
03How do I calculate siding area for a gable with a 6/12 roof pitch?+
For a symmetrical gable, rise is half the measured horizontal base multiplied by 6/12, then triangular wall area is base times rise divided by two. For a single-slope shed or half-gable, pitch extends across the full width instead. This is gable-end siding area, not the sloped roof surface.
04How much rake trim do I need for two gable ends?+
Each gable's sloped rake lengths are found with the Pythagorean theorem from the horizontal run and vertical rise. The tool totals the matching gables and, when a supplier trim stock length is entered, rounds each rake separately into whole sticks. Verify manufacturer splice and offcut rules before buying.
05Can I measure an off-center gable peak?+
Yes. Select offset-peak, measure the full horizontal base, vertical height and the peak's horizontal distance from the left base edge. The two rake lengths can differ even though triangular siding area still equals half the base times vertical height. This mode does not infer both slopes from one roof pitch.
06What does the shed gable option include?+
It calculates the triangular wall portion beneath one roof slope extending across the full measured base, with one sloped rake and one vertical edge. Shed pitch uses the full-width run, unlike a symmetrical gable which uses half-width run. Other rectangular wall parts must be measured separately.
07Does the gable siding cost calculation include labor and all accessories?+
No. It estimates full packages multiplied by the actual price you enter and, separately, rake trim sticks multiplied by a real unit price. A combined material and delivery amount appears only when both are priced. Scaffolding, labor, tax, flashing, soffit, fascia and other accessories are excluded.
08Are trim and starter strips included?+
No. The result covers siding area and package rounding only. Confirm trim, starter, corners, vents, and product-specific accessories separately.