Drain Heavy Rainfall,
Protect Your Foundation.
Free gutter calculators: 5-inch vs 6-inch sizing from roof area and rainfall intensity, downspout counts, the quarter-inch slope rule, and seamless gutter costs. No sign-up.
Roof Pitch Watershed Factor
Steeper pitches capture wind-driven rain; we apply standard roof pitch correction multipliers.
Downspout Cross-Sections
Ensure downspout drainage capacity prevents gutter troughs from overflowing during intense downpours.
1/4" Per 10-ft Slope
Verify subtle downward grade so water moves swiftly to drop outlets without standing pools.
GutterMath Calculators
Gutter Size Calculator
5-inch or 6-inch from the roof area and rainfall intensity actually draining to it.
Downspout Calculator
How many downspouts the run needs — capacity per outlet with the 30–40 ft spacing rule.
Gutter Slope Calculator
The quarter-inch-per-ten-feet rule applied to your run — total drop, hanger count, and the range check.
Building Code & Methodology
The 5-Minute Rainfall Intensity: Why Gutters Are Sized for Storms
A gutter never carries annual rainfall — only the worst five minutes of it. The NOAA method that turns weather into a size.
The Quarter-Inch Rule: Gutter Slope Done Right
1/4 inch per 10 feet — the invisible number that decides whether gutters drain, pool, or look crooked. How to set it and prove it.
Seamless vs Sectional Gutters: Where the Money Actually Goes
Seamless costs 20–40% more and eliminates the joints where gutters fail. The cost math, the exceptions, and the DIY boundary.