John used 3.75 gallons of paint to cover 431.25 square feet of wall. How much wall did he cover with each gallon?

John covered 431.25 square feet of wall with 3.75 gallons of paint. Therefore, he covered 431.25 / 3.75 = <<431.25/3.75=115>>115 square feet with each gallon of paint. Answer: \boxed{115}.