How can I fix gutters that don't seem to catch the rain?

Hello! You don't mention what kind of gutters you have now, any high pitched areas and valleys where the water is missing the gutters, and how often you need to clean out the gutters you have. You may have to get some bigger gutters and it may take a visit from a professional to give you some ideas about what you can do. We have professionally installed seamless gutters. It helped immensely with our gutter problems--water leaking at the seams and water coming off the roof so fast in a hard downpour. It was more than installing our own gutters--which we did initially--but it's been worth every penny!

http://www.gutters-guards.com/what-causes-rain-overshoot-gutters

https://www.stltoday.com/lifestyles/home-and-garden/what-to-do-about-rain-falling-over-the-gutters/article_8fdf723c-3bc9-5518-b646-3700f626a5aa.html

They make 4 & 6” gutters and I don’t think you want to replace them with the 6” or you wouldn’t be asking on this Forum, what to do?

If you have access to a sheet metal brake, I would experiment with bending a piece of aluminum gutter-guard to make a permeable dam.

Hi Est,

A gutter guard should help the problem. Here's a tutorial that might interest you for your research. Wishing you the best.

https://www.doityourself.com/stry/stop-overflowing-gutters-with-a-gutter-splash-guard