Roof Valley Length Calculator
Estimate roof-valley length from horizontal run and pitch, then calculate total stock pieces, overlap allowance and material cost.
Default project preview
5 pieces
Length per valley
20.12 ft
Base valley length
40.2 ft
Order length
45.1 ft
Purchased length
50 ft
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Valley length = horizontal run × √(1 + slope ratio²). Total length = one valley × count. Lap and cutting allowance are added, then stock pieces are rounded up.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Roof Valley Length Calculator questions
Is a roof valley always longer than its horizontal run?+
Yes, when it rises with the roof slope. The steeper the roof, the longer the sloped valley.
Does this handle unequal roof pitches?+
No. Unequal intersecting slopes can change the valley geometry and should be measured from plans or in the field.
Why include extra length?+
Valley materials may need end laps, trimming, turn-ups and waste at ridge or eave transitions.