Estimate total drip edge for two pairs of equal measured roof edges. Choose total length, an inverse edge dimension, or pieces and quoted material cost. Use actual sloped rake lengths and net installed piece coverage.

Sum two pairs of equal roof edges.

The 2L + 2W model assumes two pairs of equal measured roof edges. Measure actual eaves and sloped rakes; a plan-view footprint can undercount. Pieces are an aggregate estimate, not a cut plan.

Related Calculators

Drip Edge Formula

The following formula sums two equal edges of length L and two equal edges of length W. It does not describe every roof perimeter or add overlap and waste.

DE = (2 × L) + (2 × W)

Variables:

  • DE is the measured edge total before waste or laps (feet)
  • L is the measured length of one of two equal roof edges (feet)
  • W is the measured length of one of the other two equal roof edges (feet)

To calculate the total length of drip edge needed, multiply the length of the roof by 2, then multiply the width of the roof by 2. Add these two results together to get the total length of drip edge needed.

What is a Drip Edge?

A drip edge is a metal flashing or strip installed at the edges of a roof to direct water away from the fascia and into the gutters. It is designed to prevent water damage to the roof deck, fascia, soffit, and the home’s foundation. It also helps to protect shingles from water damage and prevents wind-driven rain from getting underneath the roof covering.

How to Calculate Drip Edge?

Measure the actual edges requiring drip edge. U.S. Department of Energy guidance addresses eaves, rakes and joint laps. For roofs with additional edges or unequal runs, sum the actual runs separately; do not assume the horizontal footprint equals the roof-edge total.

  1. First, determine measured edge length L in feet.
  2. Next, determine measured edge length W in feet, including slope where applicable.
  3. Next, use the formula DE = (2 * L) + (2 * W) to calculate the total length of drip edge needed (DE) in feet.
  4. Finally, calculate the Drip Edge.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

length of the roof (L) = 20 feet

width of the roof (W) = 15 feet

For two edges of each length, DE = 2 × 20 + 2 × 15 = 70 feet. In Pieces and material cost mode, an illustrative 10% waste allowance and 10-foot net coverage give ceiling(77 / 10) = 8 pieces. Enter a current quote to calculate material cost.