Bouldering difficulty scales explained » climber's guide
What makes a boulder problem hard?
The difficulty of a boulder problem comes from a mix of different factors:
Physical strength and core
Technical requirements (e.g., dynos, slabs, crimps, volume)
Coordination and flow of movement
Mental challenge (e.g., height of the first hold or a complex solution)
External conditions like rock quality, temperature, or lighting
In bouldering, no climbing ropes are used – so the way down almost always means jumping or falling onto a crash pad, though sometimes you can climb down. This makes it even more important to accurately assess difficulty grades.
Do bouldering and sport climbing have different difficulty grades?
Yes – and they differ significantly. Even though some rating systems look similar (like the French scale in sport climbing and the Fontainebleau scale in bouldering), they indicate completely different demands:
Bouldering is about short, explosive movement sequences with maximum intensity. Strength, technique, and power are key.
Sport climbing requires you to climb longer distances on rope – here, endurance, strategy, and mental strength over many moves are what really count.
So a 5.12a in climbing doesn’t correspond to a V8 in bouldering. The numbers tell you something about the difficulty level in both disciplines, but under completely different conditions.
If you want to know more about difficulty scales in climbing, you can check out our in-depth guide on the topic.
Common bouldering scales
When you start bouldering regularly, you'll quickly encounter different rating systems, depending on whether you're in an American gym, outside on rock, or climbing overseas. Two scales have become established worldwide: the Fontainebleau scale and the V-scale. Both have their quirks, but the goal is always the same: to assess a boulder problem's difficulty as realistically as possible.
The Fontainebleau scale: The European standard
The Fontainebleau scale (Fb) is the best-known rating system throughout Europe. It was developed in the famous bouldering area of the same name in France, and is now considered the international standard for rating boulder problems on natural rock – though it's also used in many gyms. It ranges from 1 (very easy) to 9a (extremely hard).
Starting at 6a, we're talking about advanced bouldering – which naturally requires considerable technique and strength. The difficulty is indicated by letters, sometimes with an optional "+" added:
Fb Grade | Description |
3-4 | Very easy to easy |
5a-5c | Simple to moderate |
6a-6c+ | For advanced climbers |
7a-7c+ | Challenging |
8a-9a | Pro level |
So a 7a+ is harder than a 7a, but easier than a 7b. That being said: What sounds simple may feel completely different depending on your individual boulder style.
The V-Scale: The American system
In North America, the so-called V-scale is widespread – named after the boulderer "Vermin" (John Sherman). It starts at V0 and currently goes up to V17.
Unlike the Fb scale, there are no letters or “+” additions:
V Grade | Description |
V0 | Easy |
V3 | Advanced |
V6 | Very challenging |
V10 | Pro |
V17 | World class |
Conversion Table: Fontainebleau vs. V-Scale
If you boulder in both Europe and North America – or are just curious about how the systems compare – a conversion table can be helpful. It gives you a rough orientation for what V-grade to aim for if you're used to a certain Fb grade (or vice versa).
Fb Grade | V Grade | Description |
4 | V0 | Beginner |
5a | V1 | Easy |
6a | V3 | Advanced |
6c+ | V5 | Challenging |
7b | V8 | Very hard |
8a | V11 | Pro level |
9a | V17 | Absolute world class |
One thing to keep in mind: While this conversion table can be handy to give you a general idea about difficulty levels, it's not an exact science.
Style makes the difference: Traverses, highballs & more
Bouldering is incredibly varied. Not every boulder demands the same skills from you – depending on style and orientation, completely different physical and mental strengths are required. Some boulders will push your endurance to the limit, others demand explosive power or a super refined technique. Here's an overview of the different boulder types and what you can expect:
Traverses (sideways movements): often endurance-based, usually graded lower in difficulty
Highballs (tall boulders): psychologically demanding due to height
Mantles: topping out on a ledge – technically challenging
Dynos: jumps – explosive and mentally demanding
Slabs: balance counts more than strength
This type of variety makes bouldering exciting – but also hard to compare.
How can I tell a boulder's difficulty grade?
Before you even know whether you're looking at a V2 or a V8, you first need to be able to identify or "read" the boulder – and this varies by location:
In the gym, boulders are usually color-coded. This means all holds on a route have the same color, and you'll find the rating on a small sign at the start – like "V4" or "6b+". Some gyms also use a color-coded point system or numbers by color (e.g., blue = intermediate, red = hard). The system can vary, so it's worth checking the key – especially if you're climbing in a gym for the first time.
Outside on rock looks, it’s a completely different story. Here, you won’t find any colored holds, and there’s usually no signage either. To find boulder problems, you need either a guidebook (topo) or an app. These show you the lines, difficulty grades, and sometimes even provide helpful comments or videos.
Especially outside, it's important to prepare well and be respectful of your natural surroundings, rock, and other climbers.
Why the same difficulty levels feel completely different
You’ve made it past a V4, but the next V4 boulder looks impossible? This can be due to various factors:
Route style: powerful vs. technical
Location: gym vs. outdoor rock
Daily form: sleep, energy, motivation
Route setter: every boulder route is individually set
Height and reach: affect movement options
In short: A boulder grade is a guideline, but not an absolute truth.
Indoor vs. outdoor: Differences in ratings
Bouldering indoors or outdoors is more than just a question of weather or location. The way a boulder is rated can also differ significantly depending on your environment. In the gym, you’ll enjoy the benefits of clearly defined colors, a controlled atmosphere, and routes that are set out consistently. Outside, however, is where you’ll experience the real adventure – with rock, wind, sun, and all the surprises that come with the territory. No wonder a V3 problem can feel completely different depending on the location.
Aspect | Indoor | Outdoor |
Holds | artificial, clearly marked | natural, sometimes hidden |
Rating | often "generous" | sometimes conservative |
Environment | constant, dry, climate-controlled | weather-dependent, variable |
Psychology | predictable landing | highballs & unpredictable moves |
Many gyms are customer-friendly in their grading, which can lead to surprises outside.
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Using rating systems as a guide
Whether V5 or 6c+: The difficulty grade is only part of the game. What matters is that you grow from your projects, challenge yourself, and have fun.
Scales help you better assess your level, monitor your progress, and choose appropriate boulders. But they don't replace your feel for movement – and sometimes your personal sense of achievement counts more than any number. So lace up your shoes, grab your chalk bag, and hit those walls in style!