What makes the classic trail hard, which day is the test, and how the trek you book changes the load on your back.
See the trek we recommend →Four days and 42–46 km sounds easy: about 11 km a day, less than most people walk on a city break. What makes the classic trail hard is height, not length. You start at Km 82 at 2,720 m, sleep at 3,000–3,600 m for two nights, cross Dead Woman's Pass at 4,215 m and a second pass at about 4,000 m, and finish at Machu Picchu at 2,430 m. Every step above 3,000 m costs more breath than the same step at home, and the trail is built as stone staircases rather than a graded path.
Day one is the warm-up. About 12 km along the Urubamba river from Km 82 to the first camp at roughly 3,000 m. Pickup from Cusco is between 4:00 and 6:00 AM depending on the trek, so the hardest part of day one is the early start.
Day two is the test. 10–11 km on most treks: roughly 7 km up to 4,215 m, then about 3 km steeply down to Pacaymayo at 3,600 m. One listing gives day-two temperatures of 3–20 °C — you start in a T-shirt and finish in a down jacket.
Day three is the longest. Around 16 km over the second pass at about 4,000 m, past Runkurakay, Sayacmarca and Phuyupatamarca, then down to Wiñay Wayna at about 2,650 m — more than 1,300 m of descent, most of it on original Inca steps. This is the day for knees rather than lungs.
Day four is short and early. About 6 km in the dark to the Sun Gate at 2,720 m, then down into Machu Picchu for the guided visit. The walking is easy; the pre-dawn wake-up is not.
What the trek you book changes. The trail is the same on every trek; the load is not. On the two most-reviewed treks a porter carries 7 kg of your gear, others carry 5 or 6 kg, and four treks include no personal porter at all — they sell one as an extra, so without it everything you need for four days is on your back. A private toilet tent, a sleeping bag in the price and the panoramic train home don't make the climb shorter, but they decide how rested you are for it.
Altitude is the part to plan for. Cusco itself sits at about 3,400 m. Give yourself at least two nights there before day one, walk slowly on the first afternoon, and drink more water than feels necessary. The trail never goes high enough for technical climbing, but 4,215 m is high enough that headaches and shortness of breath are normal on day two; a guide who has walked it hundreds of times sets the pace for exactly this reason.
Who finishes. The trek is walked every day by people who are not athletes. A recent review on the recommended trek mentions children aged 9 to 15 in the group, while listings set their own minimum ages — from 5 years on one trek to 16 on another. If you can walk five or six hours with a daypack on consecutive days, including long flights of stairs, you have the fitness it asks for; the rest is altitude and patience.
Moderate to hard, because of altitude rather than distance.
Day two.
Fit enough to walk five or six hours with a daypack on consecutive days, including long staircases.
Mild symptoms are common on day two at 4,215 m.
Yes, on treks that accept them.
Some sections run along steep drops, and the steps are uneven.
Your daypack, plus whatever the porter doesn't take.
Yes, most on day three's long stone descent.