Drip Edge Calculator
Calculate how much drip edge flashing your roof needs. Enter the building footprint to get the total perimeter, corner overlaps and the number of 10-foot pieces to buy.
Inputs
Standard drip edge comes in 10 ft sticks; some suppliers sell 8 ft or 12 ft lengths.
Results
Drip Edge Pieces Needed
- Roof Perimeter
- With Waste
- Strip Length Used
What would you like to calculate next?
Enter your roof length and width, then press Calculate.
How Much Drip Edge Do You Need?
Drip edge is the L-shaped metal flashing along the roof edges that keeps water away from the fascia and deck. It runs along both the eaves (horizontal edges) and the rakes (sloped gable edges) — which together form the roof perimeter.
Drip Edge Formulas
Perimeter
2 × (50 + 30) = 160 ft
Corner overlaps
160 + 4 = 164 ft
Pieces
164 × 1.10 ÷ 10 = 18.04 → 19
Worked Example
A 50 × 30 ft roof has a 160 ft perimeter. Adding one foot of overlap at each of the four corners gives 164 ft. With 10% waste that is 180.4 linear feet — divide by 10 ft strips and round up, so buy 19 pieces (about 190 linear feet of material).
Eaves vs Rakes
| Edge | Where | Drip Edge Type |
|---|---|---|
| Eave | Horizontal bottom edges (water runs off here) | Standard drip edge, installed over underlayment |
| Rake | Sloped gable edges | Same profile, installed under underlayment |
| Corners | Where eave meets rake | Overlap the pieces about 1 ft and seal the joint |
What You Need
Your roof footprint length and width — the same dimensions you would enter in the Roof Area Calculator — plus the stick length your supplier carries (10 ft is standard in most of the US).
Assumptions & Limitations
Assumes a simple rectangular footprint with four corners. Roofs with wall intersections, dormers or multiple sections will need additional flashing beyond this estimate. Gable rake overhangs longer than the eave line are not modeled. Planning purposes only.
Frequently Asked Questions
Is drip edge measured in linear feet?
Yes — drip edge is sold by length, not area. You need roughly the roof perimeter in linear feet, plus overlap at corners.
Can I reuse old drip edge?
Generally no. Old flashing is usually bent, rusty or nailed through. Drip edge is inexpensive relative to the rest of the roof, so replacing it is standard practice.
Does drip edge go under or over the underlayment?
At eaves, drip edge goes under the underlayment; at rakes it typically goes over. Follow the shingle manufacturer's installation instructions and local code.
Related Calculators
Starter Strip Calculator
Calculate starter strip rolls from your eave length, using self-adhered starter rolls or three-tab shingles cut into starter pieces.
Ridge Cap Calculator
Calculate ridge cap bundles from ridge and hip lengths, using specialty ridge cap coverage or three-tab shingles cut on site.
Roofing Material Calculator
Estimate all roofing materials: shingles, underlayment, starter strip, ridge cap, drip edge and roofing nails from your roof dimensions.
Sources & Methodology
- NRCA — National Roofing Contractors Association, Roofing Manual: Steep-slope Roof Systems — industry-standard roof geometry, roofing square and installation conventions
- Manufacturer installation instructions (asphalt shingle & metal roofing systems) — bundles per square, fastener schedules and accessory coverage vary by product — always confirm against the product data sheet
- ASTM D3462 — Standard Specification for Asphalt Shingles Made from Glass Felt — asphalt shingle product specification referenced by manufacturer installation instructions
Quantity dataset p2-data-1 (manufacturer packaging specifications, reviewed quarterly).
Formulas, assumptions and rounding rules: Methodology · Last updated: September 2026 · Calculation Engine: p1-v1 · Published by the RoofCalcWorks Editorial Team.