My house is approximately 40 ft wide by 20 ft deep = 800 sq ft
480 in x 240 in = 115,200 sq in or
800sq ft x 144sq in = 115,200 sq in
1 in x 115,200 sq in = 115,200 cubic inches of water
1 Gallon = 231 cubic inches
115,200 cubic inches/231 cubic inches = 498.7 gallons of water
Extend all downspouts far enough away from your house to be sure no water runs back towards the foundation. You can get flexible gutter extensions at your local hardware store.
Inspect and clean your gutters regularly. Water should flow freely towards the downspouts.
Inspect and clean any underground drainage to be sure water is flowing away from your house and is not backing up due to a clog.
Make sure your gutters are sloped towards your downspouts so that water doesn’t pool in the gutters.
Make modifications to your landscaping to be sure water is not flowing back towards your foundation. Remove vegetation, check for things that cause dams like edging, sidewalks, patios or fencing.