Calculate how many bundles of ridge cap shingles you need from the linear feet of ridges and hips on your roof, plus caps, nails, and estimated cost.
Ridge Cap Shingle Formula
B = ((RL + HL) * (1 + W/100)) / C
P = ((RL + HL) * (1 + W/100) * 12) / E
H = (BW/2) * sqrt(2 + (p/12)^2)
- B is the number of bundles of ridge cap shingles to buy (rounded up)
- RL is the total ridge length in feet
- HL is the total hip length in feet
- W is the waste factor as a percent
- C is the coverage of one bundle in linear feet
- P is the number of individual caps (pieces) needed (rounded up)
- E is the cap exposure in inches
- H is the length of one hip in feet, BW is the building width in feet, and p is the roof pitch as rise per 12 inches of run
The first formula drives the main mode of the calculator. It adds the ridge and hip lengths, applies a waste factor for cuts and end caps, and divides by the coverage of one bundle to return how many bundles to buy. The second formula converts the same adjusted length into individual caps using the exposure, which is the portion of each cap left visible after the next cap overlaps it. The calculator also multiplies the cap count by the nails per cap (2 standard, 4 in high wind areas) to give a nail count.
If you do not know your ridge and hip lengths, the estimate mode uses the third formula. On a rectangular hip roof with equal pitches, each of the four hips runs diagonally from a corner up to the ridge, so its length depends on half the building width and the roof pitch. The ridge on that same roof is the building length minus the building width. The reverse mode works in the other direction and tells you how many linear feet a given number of bundles will cover.
Bundle Coverage and Hip Length Reference
Coverage per bundle depends on the cap type and its installed exposure. These are typical values for common products; the wrapper on your specific bundle is the final word.
| Cap type | Pieces per bundle | Exposure | Coverage per bundle |
|---|---|---|---|
| Caps cut from 3-tab shingles | 78 (26 shingles x 3) | 5 in | About 32.5 lin ft |
| Standard hip and ridge (e.g. GAF Seal-A-Ridge) | 45 | 6-2/3 in | 25 lin ft |
| High-profile premium (e.g. GAF TimberTex, OC DecoRidge) | 30 | 8 in | 20 lin ft |
| CertainTeed Shadow Ridge class | varies | varies | About 30 to 33 lin ft |
The next table solves the hip length formula for you. It shows the length of one hip in feet by building width and pitch on a rectangular, equal-pitch hip roof. Multiply the value by 4 for the total hip length, then add the ridge (building length minus building width).
| Building width | 4/12 | 6/12 | 8/12 | 10/12 | 12/12 |
|---|---|---|---|---|---|
| 24 ft | 17.4 ft | 18.0 ft | 18.8 ft | 19.7 ft | 20.8 ft |
| 28 ft | 20.3 ft | 21.0 ft | 21.9 ft | 23.0 ft | 24.2 ft |
| 30 ft | 21.8 ft | 22.5 ft | 23.5 ft | 24.6 ft | 26.0 ft |
| 32 ft | 23.2 ft | 24.0 ft | 25.0 ft | 26.3 ft | 27.7 ft |
| 36 ft | 26.2 ft | 27.0 ft | 28.1 ft | 29.5 ft | 31.2 ft |
| 40 ft | 29.1 ft | 30.0 ft | 31.3 ft | 32.8 ft | 34.6 ft |
Example Problems
Example 1: gable roof. Your roof has a single ridge measuring 42 feet and no hips. You are using standard hip and ridge caps that cover 25 linear feet per bundle at a 6-2/3 inch exposure, with 10% waste. Adjusted length = 42 x 1.10 = 46.2 linear feet. Bundles = 46.2 / 25 = 1.85, so you buy 2 bundles. Caps = (46.2 x 12) / 6.667 = 83.2, so you need 84 caps, which takes 168 nails at 2 nails per cap.
Example 2: hip roof. The building measures 40 by 30 feet with a 6/12 pitch, and you plan to cut caps from 3-tab shingles. Ridge = 40 – 30 = 10 feet. Each hip = (30/2) x sqrt(2 + 0.25) = 15 x 1.5 = 22.5 feet, and four hips total 90 feet. Total length = 100 feet, and with 10% waste you need 110 linear feet. A bundle of 3-tab yields about 32.5 linear feet of caps, so 110 / 32.5 = 3.4, which rounds up to 4 bundles. At a 5 inch exposure that is 264 caps and 528 nails.
FAQ
How many linear feet does a bundle of ridge cap shingles cover?
Most dedicated hip and ridge bundles cover 20 to 33 linear feet. Standard products such as GAF Seal-A-Ridge cover 25 linear feet with 45 pieces per bundle, while thicker high-profile caps such as TimberTex cover about 20 linear feet with 30 pieces. A bundle of 3-tab shingles cut into caps yields roughly 32.5 linear feet at a 5 inch exposure. Coverage is always printed on the bundle wrapper, so verify it before ordering.
Can you cut 3-tab shingles into ridge caps?
Yes. A 36 inch 3-tab shingle cuts into three 12 inch caps, and installers usually taper the cut slightly so the hidden portion is narrower than the exposed portion. Cut 3-tab caps are only a good match on a roof shingled with 3-tab of the same color. On architectural (laminated) shingle roofs, use the manufacturer’s matching hip and ridge product instead: cut 3-tab caps look flat against the thicker field shingles, and mixing brands or products can void the wind coverage in the shingle warranty.
What nails should you use for ridge caps?
Ridge caps sit over more layers than field shingles, so use longer roofing nails, typically 1-3/4 to 2 inches, so the nail still penetrates the deck by at least 3/4 inch. Each cap gets 2 nails, one on each side, placed so the next cap covers the nail heads. In high wind regions, codes or manufacturer instructions may call for 4 nails per cap plus a dab of asphalt roof cement over the exposed nails on the final cap.
