Add up the linear feet of every ridge line and every hip line on the roof. Divide that total by the product's coverage per bundle, printed on the wrapper or data sheet. Add a waste allowance, then round up to whole bundles.
What do you measure on a roof?
Ridge caps cover the lines where two roof faces meet. Measure two kinds of lines and record each one separately.
Ridge lines run horizontally along the peak. Hip lines run down the slope where two faces meet on a hip roof or a dormer. Both take caps, and both count in the same total.
| Roof shape | Measure |
|---|---|
| Gable | The main ridge, from rake edge to rake edge |
| Hip | The main ridge plus every hip, from ridge end down to the eave |
| Gable with dormers | The main ridge plus each dormer ridge and dormer hip |
Measure along the roof surface, following the slope, not the flat plan distance. For a hip, run the tape from the top of the hip down to the eave edge.
How do you take the measurements?
On the roof, hook the tape at one end of the line and walk it straight along the peak or hip. Record to the nearest inch. Measure each line alone, then add the readings.
From building plans, read the scaled ridge and hip dimensions and multiply by the plan scale. Confirm one plan dimension against the building before trusting the rest.
A laser measure works for straight ridge runs from a safe stance. It reads line of sight, so take the reading along the roof line itself, not from the ground below it.
Write down the product you plan to buy before ordering. Two products with different exposures need different bundle counts for the same total length.
How much does one bundle cover?
Ridge cap shingles sell by the bundle, and coverage is measured in lineal feet, not square feet. GAF states its hip and ridge products cover 20 to 33 lineal feet per bundle, depending on the product and the installed exposure.
| Product | Pieces per bundle | Exposure | Coverage per bundle |
|---|---|---|---|
| GAF Seal-A-Ridge | 45 | 6 2/3 in | 25 linear ft; 4 bundles cover 100 linear ft |
| GAF Seal-A-Ridge AS / IR | 60 | 5 in | 25 linear ft; 4 bundles cover 100 linear ft |
| GAF TimberTex | 30 | 8 in | About 20 linear ft (30 × 8 in = 240 in) |
| Cut 3-tab shingles (estimated) | Varies by bundle | About 5 in | About 34 linear ft from a 27-piece bundle (81 caps × 5 in) |
Coverage follows from piece count and exposure. The product wrapper and the current data sheet control the accepted figure on a real project; use this table as a planning reference only.
Bundles = total measured length ÷ coverage per bundle, rounded up
Pieces needed = total measured length ÷ (exposure in inches ÷ 12), rounded up
Worked example: gable roof
A gable roof has one 42 ft ridge and no hips. The plan uses Seal-A-Ridge caps at 25 linear ft per bundle and 6 2/3 in exposure. The lengths below are worked fixtures, not project quantities.
Total lines: 42 ft. With a 10% allowance for the starter piece and cuts: 42 × 1.10 = 46.2 ft. Bundles: 46.2 ÷ 25 = 1.85, rounded up to 2 bundles.
Piece check: 42 ÷ (6.667 ÷ 12) = 75.6, rounded up to 76 pieces. Two bundles hold 90 pieces, so the count holds.
Worked example: hip roof
A hip roof has a 28 ft ridge and 4 hips of 16.5 ft each. Total lines: 28 + 66 = 94 ft. With a 10% allowance: 94 × 1.10 = 103.4 ft. Bundles: 103.4 ÷ 25 = 4.14, rounded up to 5 bundles.
Piece check: 103.4 ÷ (6.667 ÷ 12) = 186.1, rounded up to 187 pieces. Five bundles hold 225 pieces, so the count holds.
Common ridge cap measurement mistakes
- Measuring only the ridge on a hip roof and forgetting the hips.
- Using the flat plan length instead of the sloped surface length.
- Reading bundle coverage in square feet. Caps sell in lineal feet.
- Using one product's coverage figure for another product.
- Skipping the waste allowance. Hips need angled cuts and each run starts with a cut starter piece.
- Ordering exact bundles without rounding up. Caps do not sell in fractions.
Safety and professional scope
Roof work puts you at height. Measure from the plans or a ladder position when the roof is steep, wet, or unfamiliar. A tape measurement never justifies standing on a pitch you cannot walk safely.
This worksheet plans quantities. It does not approve the roof structure, the staging layout, or the fall protection plan. Those decisions follow the project documents, applicable law, site conditions, and the responsible people.
Sources and scope
- GAF, All about Hip and Ridge Cap Shingles: hip and ridge bundles cover 20 to 33 lineal feet; Seal-A-Ridge 45 pieces per bundle at 6 2/3 in exposure covering about 25 lineal feet. Accessed 2026-10-19.
- GAF Seal-A-Ridge Sell Sheet, RESHR112-1124: 6 2/3 in exposure, about 12 in wide, 4 bundles cover 100 linear feet, 45 caps per bundle; AS/IR variant at 5 in exposure, 60 caps per bundle, 4 bundles cover 100 linear feet. Dated 01/2025. Accessed 2026-10-19.
Scope: the worked examples use the two published GAF coverage figures and a 10% planning allowance; the lengths are calculation fixtures, not project quantities. The wrapper label and the current product data sheet control the accepted bundle coverage on a real project. Coverage for other brands comes from their own data sheets.
Review responsibility: Saleem Sial owns the published calculation, source, and editorial checks. Waseem Sial, External Reviewer and Engineer, remains listed for ongoing external review; no completed external-review date is claimed.
Next, plan the rest of the roof with the roofing squares and bundles guide, set the spare stock with the roofing waste allowance guide, or measure the roof area with the roof-area measurement guide.
