Ridge Cap Quantity Calculation: A Complete Worked Example

With the roof measured and the product chosen, the quantity math runs through five lines: the measured total, the product's coverage figure, the waste allowance, the bundle count, and a piece-count cross-check. This example works every line for a hip-roof house so you can compare your own worksheet against checked numbers.

How do you turn measured ridge and hip lines into a bundle order?

Add the length of every ridge line and every hip line, then add a stated waste allowance. Divide that length by the chosen product's coverage per bundle and round up to whole bundles. Cross-check the bundle count against the piece count the coverage figure implies. For the house in this example, the result is 4 bundles.

What does the example house look like?

The example is a one-story house with a hip roof. All lengths are worked fixtures for this example, not project quantities.

Hip lines run down the slope from the ridge end to the eave, measured along the roof surface. For a hip roof, leaving the hips out of the total is the most common reason an order comes up short. See the ridge cap measuring guide for how to take each reading.

Which product figures does the example use?

The example uses GAF Seal-A-Ridge cap shingles. The GAF Seal-A-Ridge sell sheet (RESHR112-1124, dated 01/2025) states 45 pieces per bundle at 6 2/3 in exposure, with 4 bundles covering 100 lineal feet, which is 25 lineal feet per bundle. That 25 ft figure is the coverage number every division below uses. On a real order, the current data sheet or bundle wrapper for the chosen product controls the accepted figure.

How does the calculation run, step by step?

1. Add the measured lines. 30 + (4 × 14.5) = 88 ft of ridge and hip.
2. Add the waste allowance. This roof has four hips with angled cuts and a starter piece for each run, so a 10% allowance is recorded on its own line: 88 × 1.10 = 96.8 ft.
3. Divide by the coverage and round up. 96.8 ÷ 25 = 3.872, which rounds up to 4 bundles. Bundles sell whole, so always round up.
4. Cross-check the pieces. Exposure is 6 2/3 in, or 0.556 ft per piece. Pieces needed = 96.8 ÷ 0.556 = 174.24, rounded up to 175 pieces. Four bundles hold 4 × 45 = 180 pieces, so the count holds with 5 spare pieces.
5. Write the order record. Product name, color, 4 bundles, the 25 ft per bundle figure, and the 10% allowance all go on one record so the crew and the supplier see the same numbers.

Bundles = measured total × (1 + allowance) ÷ coverage per bundle, rounded up

Does the same method work for a gable roof?

Yes. A gable roof in the same example set uses GAF TimberTex caps: 30 pieces per bundle at 8 in exposure, giving 20 lineal feet per bundle from a retailer listing quoting GAF specifications. The ridge measures 44 ft and there are no hips.

1. Measured total: 44 ft.
2. Allowance: 44 × 1.10 = 48.4 ft.
3. Bundles: 48.4 ÷ 20 = 2.42, rounded up to 3 bundles.
4. Piece check: 8 in exposure is 0.667 ft. 48.4 ÷ 0.667 = 72.6, rounded up to 73 pieces. Three bundles hold 90 pieces, so the count holds.

Only the measured length and the product figures changed. The method is the same for any roof shape and any cap product.

Which worksheet mistakes should you watch for?

• Measuring only the ridge on a hip roof and leaving out the hips.
• Using the flat plan length instead of the sloped surface length.
• Using one product's coverage figure for a different product.
• Recording the measured length and the allowance as one unexplained number.
• Rounding the bundle count down or to the nearest whole instead of up.
• Reading bundle coverage in square feet. Caps sell in lineal feet.

Each of these is covered in detail in the ridge cap mistakes guide.

Safety and professional scope

Measuring a roof puts you at height. Take the readings from the plans or from a safe stance when the roof is steep, wet, or unfamiliar. This worksheet plans quantities. It does not select the cap product, approve the fall protection plan, or certify wind or warranty terms. The data sheet, the manufacturer's instructions, and the responsible people control those decisions.