Valley Calculator
Calculate valley length, flashing, and materials for roof valleys
ft
Flashing Pieces (4-ft each)
9
Extra Shingle Bundles0
Metal Flashing Area55 sq ft
Estimated Cost$152
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How to Use the Valley Calculator
Trim and component materials are often underestimated. The Valley Calculator accounts for all perimeter lengths, penetrations, and overlap to give you an accurate quantity.
- Measure all relevant linear footage: eave length, rake length, ridge length, valley length.
- Count and measure any roof penetrations: chimneys, pipes, skylights.
- Enter measurements into the calculator.
- Review the material list including overlap allowance.
- Add 5–10 % for cuts and waste on metal components.
Formula & Methodology
The Valley Calculator uses the following established formulas:
Eave Length = Total horizontal length of all eave edges
Rake Length = Total sloped length of all gable edges
Ridge Length = Total length of all ridges and hips
Valley Length = Total length of all valley intersections
Metal flashing and trim are typically ordered by the linear foot. Always add 10 % for waste and overlaps.
Frequently Asked Questions
Drip edge is a metal flashing installed along eaves and rakes to direct water away from the fascia and into the gutter. It prevents wood rot and is required by most building codes for all sloped roofs.
A standard chimney requires base flashing (around the perimeter), step flashing (up the sides), and counter flashing (set into the mortar joints). Total material depends on chimney perimeter — use our Chimney Flashing Calculator for a precise quantity.
Ridge cap shingles are pre-bent, thicker shingles designed to fold over the ridge without cracking. They provide a weathertight seal at the highest point of the roof. Using field shingles cut down is cheaper but more labour-intensive and more prone to cracking.