5-inch K-Style Gutter
- Holds about 1.2 gallons of water per foot of gutter.
- Typically handles 5,500–6,000 sq. ft. of roof area per downspout (depending on rainfall intensity).
6-inch K-Style Gutter
- Holds about 2.0 gallons of water per foot of gutter.
- Can handle 7,500–7,800 sq. ft. of roof area per downspout (again, depends on local rainfall rates).
- Ideal for larger homes, steep roofs, or regions like New England where heavy rain and snowmelt are common.
The Real-World Difference
- Capacity Increase: A 6" K-style gutter holds about 40% more water than a 5".
- Downspout Size: 5" gutters usually use 2"×3" downspouts, while 6" gutters use larger 3"×4" downspouts — which means they can drain water away much faster.
- Overflow Protection: 6" gutters dramatically reduce overflow risk during heavy storms, protecting siding, fascia, and foundations.

In short:
If your home has a steep roof pitch, lots of valleys, or sits in an area like Wolfeboro or along Lake Winnipesaukee with intense rain and snow melt, 6" gutters are worth the upgrade for peace of mind and long-term protection.