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Flashing Calculator

Estimate total flashing linear feet by valleys, edges, penetrations, and drip edge for your roof

Units

Total Flashing

219 ft

10-ft Pieces

22

Cost

$328

Total Flashing Needed

219

linear feet

Breakdown

Valleys32 ft
Step/Rake Edges60 ft
Chimney10 ft
Skylights12 ft
Drip Edge80 ft
Net Total194 ft

Purchasing

10-ft Pieces

22

Cost

$328

What You'll Need

3PLUS 15 Degree Coil Roofing Nailer

3PLUS 15 Degree Coil Roofing Nailer

$120-$1704.5
View on Amazon
Guardian Rooftop Safety Kit 50ft Lifeline

Guardian Rooftop Safety Kit 50ft Lifeline

$45-$654.6
View on Amazon

Albion B-Line Manual Cartridge Caulking Gun 10oz

$32-$384.7
View on Amazon
3PLUS 15 Degree Coil Roofing Nailer

3PLUS 15 Degree Coil Roofing Nailer

$120-$1704.5
View on Amazon
Guardian Rooftop Safety Kit 50ft Lifeline

Guardian Rooftop Safety Kit 50ft Lifeline

$45-$654.6
View on Amazon

Albion B-Line Manual Cartridge Caulking Gun 10oz

$32-$384.7
View on Amazon

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Example Calculations

1Standard Ranch Roof (2 valleys, chimney, 1 skylight)

Inputs

Valleys2 x 16 ft
Edges60 ft
Chimney10 ft perimeter
Drip Edge80 ft

Result

Total Flashing204 ft

Net total of 182 ft plus overlap and 10% waste.

2Simple Gable (no valleys, no chimney)

Inputs

Valleys0
Edges40 ft
Drip Edge100 ft

Result

Total Flashing156 ft

Edges plus drip edge with overlap and waste.

Frequently Asked Questions

Q

How do I calculate how much roof flashing I need?

Measure each valley length, step/rake edge, chimney perimeter, skylight perimeter, and drip edge run separately. Sum all measurements, then add 10% for overlap and waste.

  • Valley flashing: measure the full valley length from ridge to eave
  • Step flashing: count each roof-to-wall joint in linear feet
  • Chimney: measure full perimeter including cricket/saddle behind
  • Drip edge: measure the full eave and rake edge perimeter
Q

What is the standard overlap for roof flashing?

Flashing pieces should overlap 3-4 inches minimum. In high-rain or snow areas, use 6-inch overlaps. Valley flashing should extend at least 4 inches beyond the shingle edge on each side.

  • Standard overlap: 3 in minimum for step and drip edge flashing
  • Valley flashing overlap: 4-6 in between pieces
  • Snow regions: increase to 6 in overlap to prevent ice-dam leaks
  • Always install with upper piece overlapping lower piece (water sheds downhill)
Q

What are the different types of roof flashing?

Common types include step flashing (roof-to-wall), valley flashing (where two roof planes meet), drip edge (eave and rake), and counter flashing (chimney and wall caps).

  • Step flashing: L-shaped pieces woven into shingle courses at walls
  • Valley flashing: W-shaped or flat metal running full valley length
  • Drip edge: L-profile along eaves and rakes to direct water into gutters
  • Counter flashing: mortared or reglet-mounted over step flashing at chimneys
Q

How much does roof flashing cost?

Aluminum flashing costs $0.50-$1.50 per linear foot, galvanized steel $1-$2, and copper $3-$8 per foot. Professional installation adds $5-$10 per linear foot. A typical roof with 2 valleys and a chimney needs 200-300 linear feet.

  • Aluminum: $0.50-$1.50/ft, lightweight, corrosion-resistant, easy to bend
  • Galvanized steel: $1.00-$2.00/ft, durable, standard for most residential roofs
  • Copper: $3.00-$8.00/ft, premium look, 50+ year lifespan, develops patina
  • Installation labor typically costs more than the material itself

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Last Updated: Mar 19, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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