Gutters and downspouts
Downspout length calculator
Estimate downspout pipe length. New installation/replacement.
Try the calculation
Add the vertical and horizontal route segments.
Adjustable example. Change these illustrative inputs to match your task, then recalculate. Reset restores the example and its result.
Understand the result
How this calculation works
Downspout route length adds vertical and horizontal segments before stock rounding.
Steps
- Enter the vertical route, horizontal route and stock piece length.
- Enter zero for a route with no horizontal segment.
The form starts with the worked example below. Change its values and selections to match your task; Reset restores the example.
Formula
total length = vertical + horizontal; pieces = ceiling(total length รท piece length).
Variables and units
- Vertical route (ft)
- Required. Use a positive value. Starting example: 40. Replace it for your task.
- Horizontal route (ft)
- Required. Zero is accepted. Starting example: 16. Replace it for your task.
- Piece length (ft)
- Required. Use a positive value. Starting example: 10. Replace it for your task.
What the result means
The result estimates route footage and pieces. It does not choose fittings or discharge design.
Worked example
Inputs: Vertical route = 40; Horizontal route = 16; Piece length = 10.
Calculation: 40 ft + 16 ft = 56 ft; at 10 ft pieces, 6 pieces.
Result: 56 linear ft.
Frequently asked questions
Can horizontal be zero?
Yes, for a direct vertical route.
Does it include elbows?
No.
Should I measure along the installed path?
Yes, use the route centerline or project convention consistently.