YDS Class System Explained

Let’s talk about about the Yosemite Decimal System also known as YDS. It was developed in the 1950’s by members of the Sierra Club, used to describe local hikes. Over the years, YDS has become a widespread system throughout North America to categorize the technical difficulty of hikes.

Ok – why do you need to know any of this? Well, chances are you have read my hikes and seen that each one has a Class tied to it. This is very helpful when picking out a hike you are not familiar with. Of course, distance and elevation gain are helpful dictators as to how difficult a hike might be, but equally so is the Class tied to it. Neat, so now that you know all this, let’s get into details for what exactly each class means.

Class 1: Class 1 is essentially walking. Have you been on a dirt trail before? Cool, you have hiked Class 1. Class 1 hikes almost never “require” hiking shoes/boots and can be done by basically anyone with a pulse.

Class 2: Class 2 hiking is very similar to Class 1, but sometimes involves small rock scrambles and an occasional use of your hands while on the hike. Class 2 hikes do not “require” hiking boots/shoes but they are sometimes a good idea.

Class 3: Some of my favorite hikes are Class 3. Class 3 is full on rock scrambling where using both your hands and feet are necessary. Class 3 hikes typically have some exposure and require footwear with good tread and allow you to be nimble. Class 3 hikes typically have a bit more danger associated with them.

Class 4: Class 4 hiking is essentially Class 3 but in a more vertical setting. Class 4 hikes involve the use of hands and feet on a surface where a fall would result in a serious injury or death. Class 4 hikes are almost always very exposed and require either hiking boots or shoes. A rope is sometimes used in Class 5 climbing, but usually not necessary in Class 4.

Class 5: Anything in Class 5 is considered rock climbing, if you have ever climbed using a rope (or without one) you are probably aware of this. Hikes that are Class 5 are almost always very exposed and involve vertical climbing. I won’t get into specifics since this site doesn’t focus on rock climbing, but anything after 5.9 gets broken down into a more specific rating (5.10a, 5.13d etc.) Class 5 hikes are the most technical hike you can do, but do not always require a rope. Hiking footwear is necessary and sometimes climbing shoes might be helpful to get up certain sections.

Let’s talk about a term I used in a few of the descriptions above: exposure. Exposure doesn’t mean taking off clothes to show an innocent bystander. Exposure under the YDS system means the amount of open space behind you when hiking. In other words, if you are hiking on a vertical wall, you are generally pretty exposed because there are no natural features around you and a fall would result in a serious injury. Something that is less exposed has more natural elements (trees, rocks, etc.) around you that would break your fall if that were to happen. A class 5 exposed hike means that you are essentially hiking on a rock face with nothing else around you.

Two very important things to keep in mind:

1. The YDS Class system is somewhat relative to your experience and skill level, especially when you get in the Class 3 / 4 range. If you have a ton of experience, Class 3 might feel like Class 2 but if you lack experience Class 4 might feel like Class 5.
2. The entire hike is graded off the hardest Class that it has. For example, the Crestone Traverse has one Class 5 move, but the entire hike is graded as Class 5. This is important to keep in mind when choosing a hike, because something might appear very difficult but only have one small section that makes it that way.

Hopefully this helps you on your next adventure! Questions or comments, leave them below.