Drip Edge Calculator: Pieces & Total Length

Drip edge is the metal flashing that runs along the edges of the roof to direct water off the deck and into the gutter instead of behind it. It goes on two kinds of edges: the eaves, the horizontal bottom edges, and the rakes, the sloped gable edges. Add those two lengths together and you have the total run.

Drip edge is sold in pieces, most commonly 10 feet long. So the piece count is the total edge length divided by 10, rounded up. Pieces overlap about an inch where they meet, which the waste allowance covers, and you always round up because a partial piece still means buying a whole one.

Getting the two lengths right matters. The eave length is usually easy — it is the same as your gutter run, twice the building length for a simple gable. The rake length runs up the slope, so it is longer than the flat gable width; it equals the rafter length on each side, which you can read from the roof pitch calculator, times the number of rake edges. A gable roof has four rakes, two per end.

Eave drip edge goes on first, under the underlayment; rake drip edge goes on top of the underlayment. Buy the same total either way — this tool gives you the combined count, and you can split it between the two edge types when you order.