Gutter Sizing Calculator

Calculate appropriate gutter size based on roof area and rainfall.

Surface area measurement (length × width for rectangles).
sq ft
The speed or frequency at which something occurs.
in/hr
Linear measurement in the specified unit.
ft

Results

Required Flow:
Calculated flow rate.
-gpm
Minimum Gutter Size:
Recommended size based on calculations.
-in
Downspouts Needed:
Calculated downspouts needed based on your inputs.
-
Downspout Size:
Recommended size based on calculations.
-in
Reference: Industry Standards. SMACNA gutter and downspout sizing standards.