Measured runs tell you how many pieces a roof needs. An order needs one more step: an allowance for cuts and handling, plus the product details that keep every piece in the same compatible batch. This guide converts a measured piece count into an order a supplier can fill in one delivery.
How much extra drip edge should you order?
Add 10% to the measured piece count on a simple roof and up to 15% on a roof with dormers, additions, many corners, or short runs. That allowance is a trade planning habit, not a code value. No building code sets a waste percentage, and the right number depends on the roof in front of you.
| Roof condition | Planning allowance | Why it fits |
|---|---|---|
| Simple gable or hip with few long runs | 10% | Fewer cuts and joints; most loss is the last piece of each run |
| Dormers, additions, many corners or short runs | 15% | More mitered corners and short offcuts that cannot be reused |
The per-run piece count already includes the code-required 2 in overlap at every joint. The allowance covers what overlap math cannot: cut-offs, mitered corners, kinked pieces, and re-cuts.
How do you convert measured runs into an order?
Start from the per-run piece count in the roof measurement guide, which rounds each run up to whole pieces because pieces do not span corners. Multiply the total by 1 plus the allowance, then round up again.
Order pieces = total per-run pieces × (1 + allowance), rounded up
For a 10% allowance the multiplier is 1.10; for 15% it is 1.15. Round the final count up to a whole piece.
Worked example: ordering for a gable roof
The worked example for a 40 ft by 28 ft gable roof at a 6-in-12 pitch gives 18 per-run pieces: 10 for the 2 eaves and 8 for the 4 rakes.
- Simple roof, 10% allowance: 18 × 1.10 = 19.8, rounded up to 20 pieces.
- Complex roof, 15% allowance: 18 × 1.15 = 20.7, rounded up to 21 pieces.
Check: 20 pieces at 9.83 ft of effective coverage give 196.6 ft against 142.6 ft measured. The surplus covers cut-offs and handling loss across the 6 runs.
| Run | Measured length | Pieces per run |
|---|---|---|
| 2 eaves | 40 ft each | 5 each, 10 total |
| 4 rakes | 15.65 ft each | 2 each, 8 total |
| Measured subtotal | 142.6 ft | 18 pieces |
| Order at 10% allowance | 20 pieces | |
| Order at 15% allowance | 21 pieces |
Keep this record with the order. If a shortage appears during installation, it points to the exact run that came up short.
What should the order specify?
A piece count alone does not complete an order. The supplier also needs the material, profile, selling length, finish, and thickness, with the count split by edge when eaves and rakes use different profiles. The materials guide covers how to choose these.
Drip edge is commonly sold as 10 ft pieces in single packs at retailers. Some suppliers sell by the linear foot for exact footage, which suits odd totals. Confirm the selling length on the product label before counting, because the per-run piece math changes with it.
Confirm the shipped cut length too. At least one per-foot supplier limits shipped pieces to 8 ft because long formed metal bends in transit, and offers full 10 ft lengths only for pickup or local delivery. An order planned as 10 ft pieces arrives as more, shorter pieces when the supplier cuts for shipping.
Order every piece in one batch from one supplier. Finish shades and profile bends can differ between batches, and a second order a week later can arrive visibly mismatched.
What should you check when the order arrives?
- Count the pieces against the run-by-run record before the crew starts.
- Inspect long pieces for bends and kinks. Formed metal bends easily in transit, and a kinked piece will not sit flat.
- Confirm the shipped cut length matches what the joint count assumed.
- Set aside 1 to 2 spare pieces for future repair. Matching a profile and finish years later is difficult.
Common ordering mistakes
- Dividing the total edge length by the piece length instead of rounding each run up. Pieces do not span corners.
- Using a piece count that ignored the 2 in overlap, then adding waste on top of it. Measure with overlap first, allow for waste second.
- Assuming online 10 ft pieces ship as 10 ft when the supplier cuts shipped pieces to 8 ft.
- Ordering one mixed quantity when eaves and rakes use different profiles. Count each profile separately.
- Splitting the order across suppliers or batches and getting mismatched finishes.
- Treating the 10% allowance as a guarantee instead of a planning number. Complex roofs need the higher end.
Sources and scope
- International Code Council, 2021 International Residential Code, Section R905.2.8.5 "Drip edge": adjacent segments overlapped at least 2 in (51 mm) on shingle roofs.
- 2012 IRC significant-changes summary: drip edge usually manufactured in 10 ft lengths; confirm the selling length on the product label.
- Engineer Fix, "How to calculate how much drip edge you need": 10 ft standard lengths; 1-2 in overlap per seam; 10-15% waste allowance, higher for complex rooflines (accessed 2026-10-20).
- RoofScope, "Roofing waste factor" planning table: worked 10% waste example on measured drip edge line items (accessed 2026-10-20).
- GutterAll 1x3 hemmed aluminum drip edge: sold per linear foot; 10 ft section reference; shipped pieces limited to 8 ft maximum; longer pieces via pickup or local delivery (accessed 2026-10-20).
Scope: the methods here convert measured drip edge runs into an order count and an order record. The waste allowance is a planning number from trade guides, not a code requirement. The governing code, local amendments, product label, and supplier terms control the accepted profile, fasteners, and final order.
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, read the roof measurement guide for the per-run piece method this article builds on, or the materials guide to choose the metal and profile before ordering. For the full set of planning tools, return to the Roofing Calculators hub.
