The most challenging bouldering problems require strength and technical prowess that even the best climbers can't complete immediately.

However, several athletes these days are becoming more comfortable in the V16 routes and now challenge themselves to ascend higher-ranked boulder problems.

Today, we explore the world's most challenging boulder problems and what makes them tough to climb.

Why Are Bouldering Routes Called "Problems"?

Routes are called "problems" because they are challenging to complete. They may be short, but they require great strength and agility to get up.

This difficulty is relative, and some routes may be easier than others for a given climber, but they are all challenging nonetheless.

A route's difficulty is often determined by its height, width, and exposure. For example, a problem might be considered easy if only five feet high.

But this becomes more difficult if it is fifty feet tall and requires climbers to reach the top.

How Are Bouldering Problems Ranked?

The V Scale

The V Scale is a ranking system for bouldering problems developed by pioneer boulderer John Sherman. The scale ranges from VB (Very Beginner) to V0 and above, with each number more difficult than before.

The Font Scale

Another type of scale that measures bouldering problems is the Font Scale. Also called the Fontainebleau Scale, it's a scale that starts from 1 to 6. As soon as the Font Scale hits 6, it adds some suffixes to the number to indicate difficulty changes.

Usually, the first suffix is either A, B, or C. As the letter gets later in the alphabet, it becomes more complex. Therefore, a 6C is more rigid than a 6B.

In addition, a "+" can be added after the letter to indicate a slighter change in difficulty rather than a total grade change.

Having a plus means you have a more complex problem than with no plus. 

As a rule of thumb, a 6A+ is more demanding than a 6A, while a 6B is more challenging than a 6A+.

A bouldering problem is considered hard or challenging if its V Scale grade is V15 and above, which is equivalent to 8C and above on the Font Scale.

If you're interested, you can check out our article on how bouldering problems are graded.

Where Can I Find the Hardest Bouldering Problems in America?

The most challenging bouldering problems in America can be found in some of the country's most rugged and remote areas.

Here is a table that includes the climbers who have successfully climbed the bouldering routes:

Where Can I Find Other Bouldering Problems Across the Map?

In the world, the USA tops 10 other countries with the most challenging bouldering locations globally. Switzerland ranks second with 7 boulder problems, and Japan sits third with five.

Here’s a table that lists the most challenging boulder routes in other parts of the world:

The world's most challenging boulder problems are Burden of Dreams, located in Finland, and Return of the Sleepwalker in Red Rock, USA. Both these routes have yet to have a second ascent.

As of 2022, there are currently 27 boulders with a V16 (8C+) grade. The most well-known problems under this grade are Creature From the Black Lagoon (USA), United (JP), and Off the Wagon Sit (Switzerland)

Who Decides What Grades the Bouldering Problems Are?

Typically, the climbers who ascend their boulder routes grade according to their experience. The bouldering community then often comes to a consensus on the proposed grades. 

Daniel Woods, for example, proposed Return of the Sleepwalker as a V17 in 2021. V17 is currently the highest grade for bouldering problems. 

Like the Burden of Dreams, Return of the Sleepwalker has never had a second ascent yet, making this a critical factor in its ranking.


Climbing boulders is no easy feat. As years come and go, climbers love a little more challenge, and the quest for finding challenging boulder problems continues.

Who knows? We may have another V17 or greater bouldering problems in the world soon.

Remember that while bouldering is a fun outdoor sport to engage in, climb routes within the range of your ability. Check the V Scale or the Font Scale to assess your skills according to the problem's difficulty.

If you're interested in learning more about bouldering, check out our other blog posts!