The Classic Inca Trail trek has different itineraries according to what you would like and how much time you have. The following is the difficulty level according to the trek to Machu Picchu.
Difficulty level: Easy
Maximum Altitude: 3000 m
Minimum Altitude: 2600 m
Distance travelled: 9 Km
Approximate walking Time: 5-6 hours
Difficulty level: Difficult
Maximum Altitude: 4600 m
Minimum Altitude: 3000 m
Distance travelled: 12 Km
Approximate walking Time: 6-7 hours
Difficulty level: Moderate
Maximum Altitude: 4000 m
Minimum Altitude: 2650 m
Distance travelled: 16 Km
Approximate walking Time: 8 hours
Difficulty level: Easy
Maximum Altitude: 2650 m
Minimum Altitude: 2100 m
Distance travelled: 6 Km
Approximate walking Time: 2 hours