What is the average length of time for a tennis match?

...How long is a piece of string? That's impossible to answer. It's generally the best of three sets. So if it's at two sets, it could be 6-0 6-0. Which could take under an hour. It it was 7-6 6-7 7-6, that could be two or three hours. Rain could delay play. Medics called out. Discussion on points. Injury. Toilet breaks. Tie breaks. Retirement. So many things could influence the length of a "normal ATP tennis match", so I'm afraid you can't slap a one hour time frame on it, and call it the length it takes to play.