HesapHanem

Roof Drip Edge Calculator

Enter your eave and rake lengths, piece length, and waste percentage to size the drip edge.

How it is calculated

The tool adds the two edge types and then applies your waste allowance: perimeter = eaves + rakes, length to buy = perimeter × (1 + waste/100) and pieces = ⌈length to buy ÷ piece length⌉. Eaves and rakes are total lengths in feet (the horizontal bottom edges and the sloped side edges), the piece length is in feet and waste is a percent. If you leave the piece length empty it uses 10 ft, and if you leave waste empty it uses 10%. Zero waste is accepted. The count is always rounded up to whole pieces. Overlap at joints is not modelled separately, so it is covered only by the waste percentage you choose.

Worked example

A gable roof has 80 ft of eaves and 60 ft of rakes, and drip edge comes in 10 ft pieces with 10% waste. Step 1: perimeter = 80 + 60 = 140.00 ft. Step 2: with waste, 140 × 1.10 = 154.00 ft. Step 3: 154 ÷ 10 = 15.4, rounded up to 16 pieces. Without any waste allowance, 140 ft would need 14 pieces, so the allowance adds two pieces to the order.

Try this example →

Common mistakes

  • Entering the roof area instead of edge lengths. Drip edge follows only the eaves and rakes, so square footage of the roof does not belong in either field.
  • Measuring the rake along the horizontal run instead of along the slope. A rake edge is sloped, so measure its true length, which is longer than its horizontal run.
  • Leaving the waste field empty and assuming zero waste. An empty waste field uses 10%; type 0 if you really want none.
  • Entering the piece length in inches or metres. The unit is feet, and the common piece is 10, not 120.
  • Counting edges that do not get drip edge. If part of the roof meets a wall or has no gutter edge, leave that length out so you do not over-order.

About this calculator

Drip edge is the L- or T-shaped metal flashing installed along a roof's eaves and rakes to direct water away from the fascia and into the gutter instead of behind it — required by most modern building codes at both edges. It's sold in fixed-length pieces (commonly 10 feet), and each joint needs a small overlap (typically 2 inches), so the number of pieces needed is more than a simple perimeter-length division.

This calculator takes your total eave and rake lengths, the piece length, and a waste percentage (10% if left blank), and returns both the linear feet and the number of pieces to buy. It does not calculate joint overlaps separately, so use the waste percentage to cover overlaps as well as cutting losses at corners, valleys, and hips. Roofing contractors and DIY re-roofers use it when ordering material for a roofing job, since drip edge is a small line item that's easy to under-order if you only measure the roof's raw perimeter.

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Comments (1)

  • Editorial team

    Measure rakes along the slope, not from a plan view. On a 6 in 12 pitch the sloped edge is about 12% longer than its horizontal footprint, enough to leave you short. The default waste allowance also has to cover the joint overlaps and corner cuts, which this tool does not itemise. The tool works in feet only. What roof shape are you covering: gable, hip or something more complex?

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