Skills · Reading a route
The SAC Hiking Scale (T1 to T6), explained
The Swiss Alpine Club's T1 to T6 hiking scale in plain English: what each grade means, the trail-marking colours, and what the grade can't tell you.
The Datum Heights Desk · 8 min read
Plan hikes in the Alps and one set of grades follows you everywhere: T1 to T6. It comes from the Swiss Alpine Club, and it has quietly become the common language for how hard a mountain walk is, printed on signposts, attached to routes, and used far beyond Switzerland.
The scale runs from T1, an easy walk on a well-made path, to T6, serious unmarked alpine terrain with climbing and glaciers. Six grades, plus a + that nudges any of them half a step harder. Here is what each grade means, how to read the trail markings that go with it, and, just as important, what the grade leaves out.
Key takeaways
- Six grades: T1 (easy path, no fall danger) to T6 (unmarked alpine terrain with grade-II climbing and glaciers).
- Switzerland's trail markings encode the grade: yellow for T1, white-red-white for T2 to T3, white-blue-white for T4 and above.
- The scale bundles effort, terrain, and exposure into one grade. It does not tell you how remote, how navigable, or how weather-exposed a route is.
- Treat the grade as a floor for terrain difficulty, then read the rest of the route before you commit.
The six grades at a glance
| Grade | Name | Terrain in one line | Trail marking | You need |
|---|---|---|---|---|
| T1 | Hiking | Well-made path, flat or gently sloped, no fall danger | Yellow | Any footwear; no experience |
| T2 | Mountain hiking | Marked path, steeper in places, some fall risk | White-red-white | Sure-footedness, hiking shoes |
| T3 | Demanding mountain hiking | Exposed sections, sometimes secured with chains or ropes; hands used for balance | White-red-white | A head for heights, confident footing |
| T4 | Alpine hiking | Not always a visible path; easy snow-free glaciers, steep terrain | White-blue-white | Alpine experience, terrain assessment |
| T5 | Demanding alpine hiking | Often trackless; snow, glaciers, and single climbing sections to UIAA grade II | White-blue-white | Basic ice-axe and rope skills |
| T6 | Difficult alpine hiking | Unmarked; climbing to UIAA grade II throughout, long glaciers, very exposed | White-blue-white (often none) | Full alpine competence |
Grade by grade
T1: Hiking
A well-made path on flat or gently sloping ground, with no danger of falling. The valley trail, the lakeside path, the graded route to a popular viewpoint. Any footwear will do and no mountain experience is needed. At T1, the terrain is not the thing that will stop you.
T2: Mountain hiking
A marked path with a clear line, but steeper in places, with the odd spot where a fall is not impossible. The ground is rougher than T1 and the ascents more sustained, so sure-footedness and proper hiking shoes start to matter. Most people's idea of a proper mountain walk lives at T2.
T3: Demanding mountain hiking
The path may not always be obvious, and there are exposed sections, sometimes fitted with chains or fixed ropes to hold as you pass. You may need your hands for balance. This is the grade where a head for heights becomes a real requirement, and a slip in the wrong place has consequences.
T4: Alpine hiking
Now the trail is often not visible at all, and the ground includes easy, snow-free glaciers and steep pathless terrain. You are reading the mountain rather than following a line on it. T4 asks for genuine alpine experience: the judgement to assess terrain, place your feet on rough ground, and know when to turn back. The marking, where it exists, turns blue.
T5: Demanding alpine hiking
Frequently trackless, steep, and mixed with snow, glaciers, and single climbing moves up to UIAA grade II. Basic ice-axe and rope skills come into it. This is no longer hiking with a few hard moves. It is alpine mountaineering that happens to include some walking, and the consequences match.
T6: Difficult alpine hiking
Unmarked, very exposed, with climbing to UIAA grade II throughout and long stretches over glaciers where a slip runs a long way. Full alpine competence is assumed: movement on steep ground, glacier travel, and the judgement to manage all of it. T6 is the serious end of the scale, and the grade alone should tell an honest walker whether it is their day out or not.
Reading the trail markings
In Switzerland the paint on the rocks and posts tells you the grade before you have read a single sign:
- Yellow: T1. A hiking trail, nothing technical.
- White-red-white: T2 to T3. A mountain trail, needing sure-footedness and a steady nerve where the ground drops away.
- White-blue-white: T4 and above. An alpine route, needing experience and often equipment.
If the markings turn blue and you were expecting a stroll, that is the mountain telling you the day just changed grade.
What the SAC grade does not tell you
The T-scale is good at what it measures, the terrain and exposure of the ground itself, but it bundles several things into one letter-and-number and stays silent on others.
It does not tell you how remote the route is (a T3 an hour from a car and a T3 half a day from help carry the same grade), how hard it is to navigate (marking is not the same as route-finding once you are off it), or how exposed to weather you will be. Those are the things that turn a manageable grade into a serious day.
That is why we read every route on five separate axes, physical, technical, exposure, environment, and navigation, with the SAC grade feeding the first three. For the full picture, see why one difficulty grade can't tell you enough.
How it compares to other systems
The North American YDS (Class 1 to 5) rates only the hands-on technical difficulty of the ground. Roughly, T1 to T2 sit around Class 1, T3 around Class 2, and the climbing sections of T5 to T6 reach Class 3 to 4. The systems measure different things, so treat the mapping as a guide, not a conversion.
The alpine adjectival grades (F to ED) describe a whole route's overall seriousness rather than the walking terrain, so they take over where the T-scale runs out, on genuinely technical alpine ground. For how these scales relate, see how the grading systems fit together.
Frequently asked questions
What is the SAC hiking scale?
It is the Swiss Alpine Club's six-grade scale for mountain walks, T1 (easy, well-made path, no fall danger) to T6 (unmarked alpine terrain with grade-II climbing and glaciers). It is the standard hiking-difficulty scale across the Alps and blends terrain, effort, and exposure into one grade.
What does the "+" mean in SAC grades?
A + after a grade (for example T3+) means the route sits at the harder end of that grade, roughly half a step up, without quite reaching the next full grade.
What SAC grade is right for a beginner?
T1 and T2 suit beginners: marked paths, no real fall danger at T1 and only limited exposure at T2. T3 introduces exposure and steep, sometimes secured sections, so build up to it. From T4, alpine experience and often equipment are required, which is no longer beginner territory.
Is T3 dangerous?
T3 has exposed sections where a fall would have consequences, sometimes secured with chains or ropes. It is not dangerous for a sure-footed hiker with a head for heights in dry conditions, but it is unforgiving of a slip, and wet or icy ground raises the stakes. Read the exposure, not just the grade.
The short version
The SAC scale is the Alps' common language for how hard a walk is: T1 for easy paths, up through T3 where exposure and steep, secured ground start to matter, into T4 to T6 where it becomes alpine mountaineering. Learn the marking colours, yellow, white-red-white, white-blue-white, so you can read the grade off the trail itself. And remember what the single grade leaves out: how remote, how navigable, and how weather-exposed the route is. For that, read it on all five axes.
See any route's full profile, the SAC grade plus the four axes the grade can't show, on our route pages, or work out whether a route suits you with the honest hike planner.