Adidas Ultraboost 5X review

We think that the Ultraboost 5X is a serious option for:

• Runners who love the Ultraboost series but wanted a lighter design.
• Heel strikers ready to invest in a premium shoe with luxurious materials.
• Those seeking unbeatable durability paired with a stretchy, comfy knit upper.
• Anyone unconcerned about price seeking a versatile shoe for casual runs and everyday wear.

We believe the Ultraboost 5X falls short of justifying its premium price for those concerned about performance, as it lacks the energy return found in similarly priced options like the Nike Pegasus Plus. And for better performance value, the ASICS Novablast 5 and Hoka Mach 6 provide a bouncier ride at a more affordable cost.

Additionally, we think the Ultraboost 5X may not appeal to those who prefer the classic Ultraboost design. If weight isn’t a concern and you value the traditional midfoot plastic cage for improved lockdown, the Ultraboost 5 is a better choice.

Adidas lists the Ultraboost 5X as having a 39/29 mm stack height, but our callipers measured the heel at 34.6 mm.

This height provides ample cushioning for rearfoot strikers but doesn’t align with the towering, ultra-cushioned trends of modern maximalist shoes exceeding 40 mm. It more akin a modern daily trainer, and we believe it’s the ideal choice for this shoe.

The forefoot, consistent with Adidas designs, measures a slimmer 24.2 mm compared to the heel, maintaining the Ultraboost’s reputation as a well-cushioned shoe but clearly favoring heel strikers in its design.

The difference between the two measurements results in a precise 10.4 mm drop, closely aligning with the official 10-mm offset.

In our view, this consistency highlights the Ultraboost’s beginner-friendly design, making it well-suited for slower, easier paces.

We still remember the launch of the original Ultraboost in 2015, when it was promoted as a “cloud-like” and “soft” shoe. But running shoes have evolved dramatically over the past decade, reshaping how we perceive cushioning. Interestingly, the once-plush Ultraboost now feels relatively firm, leading Adidas to refine the midsole to address both softness and weight concerns.

Instead of the classic Boost, the Ultraboost 5X comes with Light Boost, a bouncier, softer, and lighter iteration—essentially Boost 2.0 with a cool name.

According to our field tests, the shoe feels good underfoot but leans slightly firmer than our 16.4-HA measurement suggests. In our view, Light Boost—likely influenced by the outsole—offers a balanced experience rather than an overly soft one.

Light Boost remains a TPU-based foam, a material that revolutionised running in 2015 with its superior energy return compared to EVA. Its performance in cold temperatures also stood out.

However, during our 20-minute freezer challenge, we discovered that Light Boost became 34% firmer—a bad outcome for TPU. While this compound should excel in cold conditions, this result fell short of our expectations.

We discovered that Adidas has included an insole that is thinner than what we typically see in daily running shoes.

The Ultraboost 5X is not a super-rockered shoe like most recent designs in the market, but follows a more traditional approach. We found a subtle and late curvature that makes it ideal for easy runs and equally suitable for walking.

A key factor behind the rise to fame of the Ultraboost (apart from Kanye West, of course) is the cosy Primeknit upper. Unlike many other Adidas models, it delivers a generously roomy feel, thanks to its roomy toebox and ultra-stretchy knit material.

We made a gel mould of the toebox, and afterward, we took three precise measurements to better define its fit. The first, measured at the widest point of the toebox, came in at 96.2 mm. While this falls around average, the stretchable knit gives it a slightly more accommodating feel.

We were pleasantly surprised by the minimal taper of the toebox. Measuring 75.4 mm in this area, we can confidently say that the Ultraboost 5X accommodates wide feet exceptionally well, again, thanks to its highly-stretchy Primeknit material.

However, you must be comfortable with the knit resting on your toes, as the vertical space is limited at 23.9 mm.

This is a common trait of knit-based uppers, but in our experience with Primeknit, it never causes too much pressure on the toes. However, if you prefer more vertical room, the Adidas Supernova Rise may be a better fit for your needs.

The Ultraboost debuted 10 years ago, yet Adidas continues to preserve key elements of its DNA even after so long, like the plastic heel cups or the Torsion System—a X-shaped piece nestled between the outsole and midsole.

It’s visible through select outsole cutouts (search for light blue instead of white) and functions to add torsion rigidity. for a more centred stride. By reducing excessive flexibility, it ensures every step feels more controlled, and the Ultraboost 5X remains as stable as a table.

We already highlighted the Torsion System incorporated by Adidas, so it’s no surprise that the Ultraboost 5X scores an impressive 4/5 in this test—well above average.

If ultra-flexible shoes are your preference, consider the New Balance FuelCell Rebel v4 instead.

The heel counter achieves a solid balance between support and comfort, though it might feel less forgiving for runners landing slightly misaligned on the heel due to the plastic heel cups. For us, it scores a respectable 3/5.

The forefoot of the Ultraboost 5X never felt particularly wide, a clear indication that Adidas designed this shoe with heel strikers in mind. In our experience, the emphasis on rearfoot cushioning aligns with its target audience.

It’s worth noting that most Ultraboost pairs sold globally are used as lifestyle trainers rather than running shoes. While we still prefer the Ultraboost 1.0 for casual wear, the 5X will also likely see heavy use for walking. That's another reason why we think the forefoot doesn’t aim for ultra-broad dimensions—and our callipers showed 115.4 mm, just around the average.

The heel is wide and exceeds the average, measuring 94.5 mm. In our view, this design choice aligns perfectly with the Ultraboost 5X's dual-purpose role as a casual running shoe and sneaker. We also found this broader heel enhances stability and provides solid support, making it an ideal option for heel strikers.

While the UB5X feels rigid in torsional flexibility, it’s impressively pliable longitudinally—making it an excellent choice for walking. In our 90-degree bend test, we recorded a remarkably low score of 18.5N!

The weight of the Ultraboost series has long been a negative point for us. The transition to Light Boost foam brought improvements, but the Ultraboost 5 still tipped the scales at 10.3 oz or 292g—on the heavier side for a daily trainer.

However, the Ultraboost 5X significantly improves in this aspect. With subtle yet effective modifications, it shaved down to a much reasonable 9.4 oz or 266g. In our experience, this weight reduction makes the shoe feel noticeably more agile and fun!

Knit uppers often struggle with breathability due to their dense, cosy fabric. They’re fantastic for all-day comfort but frequently fall short in airflow. The Ultraboost 5X follows this trend, offering only moderate ventilation despite its high-quality materials.

Using our smoke machine connected to a 3D-printed airflow piece, we tested the toebox ventilation and found it to be average, scoring 3/5. While this is decent for a knit upper, it falls short of expectations for a shoe at this price. The added ventilation holes in the toebox help, but they don’t completely solve the problem.

Under a microscope, we discovered that these ventilation holes are smaller and less open than they appear, limiting airflow further.

This explains why the shoe felt a bit warm during runs, even with these elements aimed at improving breathability.

On the positive side, the Primeknit upper remains a standout in terms of comfort. Its stretchy material expands easily to accommodate different foot shapes. Few shoes on the market can match its premium feel.

Another common challenge for knit uppers is durability. They’re typically smoother than mesh, making them softer on the feet but less abrasion-resistant. However, the Ultraboost 5X surprised us with an outstanding 5/5 durability score. This is fantastic news for runners worried about wearing holes near the big or pinky toe.

The heel padding also demonstrated remarkable resilience during our Dremel test. Achieving two consecutive 5/5 scores in durability tests is an extremely rare accomplishment in our lab. Congrats on this one, Adidas!

One of the standout features of the Ultraboost 5X is its use of Continental rubber across most of the outsole—a material known for delivering exceptional grip in both dry and wet conditions. 

Like we wrote in our guide about running shoe outsoles, Continental rubber is one of the few materials that genuinely overcomes the usual compromise between grip and durability faced by most compounds in the industry.

We clocked an average 79.4 HC in hardness during our first test, setting the stage for its performance against the Dremel.

As expected from Continental, the Dremel test performance was outstanding. We observed a minimal 0.4 mm dent in the rubber, placing this outsole among those built for exceptional durability.

We measured the outsole thickness at 2.6 mm, which we found reasonable considering the cutting-edge durability offered by Continental.

Positioned as one of Adidas’ flagship trainers, it prioritizes luxurious comfort and top-tier materials like Primeknit and Continental rubber over pure performance metrics. Considering its legacy and previous models, the price feels logical—Adidas has never marketed the Ultraboost line as budget-friendly, and after nearly a decade, it’s clear that affordability isn’t part of its DNA.

The UB5X includes some reflective elements, although we wish they were larger, at least on this colorway.

The integrated tongue includes a small piece to secure the laces—an unusual feature compared to previous Ultraboost designs. On the other hand, as is common in this series, only four eyelets are utilised, leading to a fit that bets everything on the adaptive and flexible knit upper.

We found that the tongue features minimal padding, measuring just 1.5 mm. This ultrathin design is best suited for runners who rarely experience discomfort on the instep.

One of the key reasons for the Ultraboost’s enduring popularity since 2015 is its amazing sock-like upper—still present in the 5X. This design eliminates a separate tongue and ensures a snug, second-skin fit that molded closely to our foot without causing uncomfortable pressure.

The Ultraboost 5X includes an extended heel collar designed to simplify slipping into the sock-like upper while providing additional support to the Achilles tendon.

We easily removed the insole and replaced it with various footbeds from other shoes without any issues.

Adidas made an unusual and confusing move by launching both the Ultraboost 5 and 5X with market-specific availability. In the US, the 5X is widely accessible, while the 5 is harder to find. In Europe, both models are available, though not in every colorway.

The differences between the two are minimal, with the most notable being the 5X’s reduced weight due to the removal of the external plastic midfoot cage. Instead, the 5X features an internal plastic support piece that somewhat maintains the midfoot's structure while saving weight at the same time.