How this calculator works
Drip edge is a strip of bent metal that sends water off the roof edge and into the gutter, and keeps it from running back under the shingles or the fascia. Each piece is 10 feet long, but it must overlap the next one, so a piece adds a little less than 10 feet to the run. The calculator takes the length of the run, takes off one overlap (the first piece does not overlap anything), and divides by the length a piece adds.
Worked example: 60 ft of eaves with 10 ft pieces and a 2 in overlap needs 7 pieces, since each adds 9 ft 10 in. With a 3 in overlap it needs 7. The default case, 100 ft of eaves and rakes together, is 12 pieces with 5% extra, and 100 nails at one a foot.
Assumptions and sources
- Assumptions used: drip edge at the eaves and rakes, overlapped at every joint; nails at no more than 12 in on center (IRC R905.2.8.5).
- The International Residential Code asks for drip edge at the eaves and rake edges of shingle roofs, overlapped at least 2 in, extending at least 1/4 in below the sheathing and 2 in up the deck, and fastened at no more than 12 in on center. The underlayment goes over the drip edge at the eaves and under it on the rakes. Local codes and shingle makers may add to this, so check yours. Count the corners and any hip, valley or wall flashing separately.
The formula and a worked example are shown above, so you can check any result by hand. Read how we calculate and check our numbers. Results are estimates for planning: supplier products vary, so check the size printed on the label.
Drip edge pieces for common roofs
10 ft pieces, 2 in overlap, 5% extra. A simple gable roof has two eaves and four rakes (two at each gable end); a hip roof has four eaves and no rakes.
| Roof | Eaves | Rakes | Pieces to buy |
|---|---|---|---|
| 24 × 30 ft gable | 60 ft | 54 ft | 13 |
| 28 × 40 ft gable | 80 ft | 63 ft | 16 |
| 30 × 50 ft gable | 100 ft | 67 ft | 19 |
| 28 × 40 ft hip | 136 ft | 0 ft | 15 |
| 30 × 50 ft hip | 160 ft | 0 ft | 18 |
Tips before you buy
- Many roofers use a different profile at the rakes (an L-shaped or "D" style) from the eaves (a "C" or "T" style), so count them separately and check the label.
- At the eaves the underlayment goes over the drip edge, and at the rakes it goes under it, so the water runs onto the shingle and not behind the metal.
- Overlap pieces in the direction of the water flow, and cut a miter or an overlap at the corners so that no gap faces up the roof.
- Use nails of the same metal as the drip edge. Mixing metals corrodes the edge, and galvanized steel in contact with copper or aluminum is a common cause.
- If you are re-roofing, check whether the old drip edge can stay. A bent or rusted piece is cheap to replace while the shingles are off.
Tools & materials for this project
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Frequently asked questions
How much drip edge do I need for my roof?
Add up the eaves and the rakes, and divide by the length a piece covers after the overlap. For 100 ft of edge with 10 ft pieces and a 2 in overlap, buy 12 pieces, which includes 5% extra.
How long is a piece of drip edge?
Most drip edge is sold in 10 ft pieces. The overlap between pieces means each one adds slightly less than its length to the run.
How much do drip edge pieces overlap?
The International Residential Code asks for at least 2 inches between adjacent pieces. Many installers use 3 to 4 inches.
Do I need drip edge on the rakes as well as the eaves?
The IRC asks for drip edge at both the eaves and the rake edges of shingle roofs. Local codes and the shingle maker's instructions may differ, so check them.
How far apart do I nail drip edge?
No more than 12 inches on center under the IRC, so about one nail per foot of edge.
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Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.