Atlanta airport is pretty easy to navigate. There are a lot of signs directing you to where you need to go, and even the Plane Train to get you between terminals faster. That being said, it is a large airport with 7 terminals. If you are up for a bit of a rush and enjoy a shorter layover, the easy navigation means you won’t have an issue making it with airline minimum layovers which are usually around 35 minutes. If you like to have time, get acquainted with the airport, stretch your legs before the next flight, 60 minutes should be enough. With international travel you should always plan for extra time in the airport in order to accommodate the extra hassles like customs.