The Adidas Ultraboost 21's standout features are premium comfort and a great fit. Its seamless upper locks in and conforms to your foot with a sock-like fit when running, and, honestly, you would have a hard time finding a more comfortable men's running shoe on the market. The enlarged heel on this model helps place your foot into a nice forefoot toe-off position and is helped by the subtle cushioning that is surprisingly smooth and responsive. With one of the heavier weights in our lineup, some may view the weight as too big of a downside to overlook, especially given its fairly hefty price tag.Editor's Note: This individual gear review was updated on March 6, 2022, to include new sections and details to help your product determination.
Adidas Ultraboost 21 Review
Compare prices at 2 resellers Pros: Comfortable, stable, supportive, unique design
Cons: Heavy, expensive
Compare to Similar Products
Adidas Ultraboost 21
|Price||$107.97 at Backcountry|
Compare at 2 sellers
|$159.95 at Amazon|
Compare at 2 sellers
|$104.00 at Backcountry|
Compare at 2 sellers
|$73.40 at Amazon|
Compare at 2 sellers
|Check Price at REI|
Compare at 3 sellers
|Pros||Comfortable, stable, supportive, unique design||Responsive cushioning, breathable upper, lightweight||Lightweight, great cushioning, comfortable upper||Responsive, light, fast affordable||Responsive cushioning, smooth heel-to-toe rocker, durable|
|Cons||Heavy, expensive||Minimal support and stability||Less responsive, lacks rubber outsole||Minimal support, lacks cushioning, lacks outsole rubber||Loose heel cup, support under heel lacking|
|Bottom Line||Premium upper design with a responsive cushioned outsole perfect for longer outings||Excellent cushioning that provides great energy transfer with an extremely comfortable, performance fit upper||These lightweight shoes have top landing comfort and maximum cushion with a great upper||A model that makes you feel quick, fast, and light that provides maximum energy transfer and forward-momentum||A rockered design with responsive cushioning keeps legs feeling powerful and fresh into longer efforts|
|Rating Categories||Adidas Ultraboost 21||Saucony Endorphin S...||Hoka One One Mach 4||Saucony Kinvara 12||New Balance Fresh F...|
|Cushioning and Landing Comfort (25%)|
|Upper Comfort (20%)|
|Lateral Stability and Support (15%)|
|Specs||Adidas Ultraboost 21||Saucony Endorphin S...||Hoka One One Mach 4||Saucony Kinvara 12||New Balance Fresh F...|
|Weight (per shoe, size 9.5)||12.9 oz.||8.3 oz.||8.1 oz.||7.7 oz.||9.4 oz.|
|Heel to Toe Drop||10 mm||8 mm||5 mm||4 mm||8 mm|
|Midsole Material||Boost||PWRRUN||PROFLY||PWRRUN||Fresh Foam|
|Sole Rubber||Continental||XT-900||Rubberized EVA||Foam with rubber inserts||Ortholite|
|Upper Material||Textile/recycled polyester||Engineered mesh||Engineered mesh||Mesh||Synthetic, mesh|
|Width Options||Normal||Normal||Normal||Normal, wide||Narrow, normal, wide, extra wide|
|Sizes Available||5 - 14||7 - 15||7 - 14||7 - 15||6 - 20|
Our Analysis and Test Results
Featuring one of the most comfortable uppers we have ever tested in our review of men's running shoes is the Adidas Ultraboost 21. A thick outsole provides ample cushioning but is firm and responsive when faster turnover is needed. The locked-in feel of the upper makes this model feel stable and supportive. Unfortunately, these features come at a cost, a higher weight of 12.9 ounces in a men's size 9.5, making this model feel a bit sluggish at times.
Cushioning and Landing Comfort
The Adidas Ultraboost 21 has excellent landing comfort with its thick, durable outsole. The rockered design of the shoe helps roll your foot into a nice toe-off position, even if you land further back than your midfoot. This is helpful when fatigue starts to set in and your form starts to break down. The rockered design also is beneficial when descending because of the added support of the heel, which takes off the stress from your Achilles and lower legs. The cushioning feels supportive and responsive, without feeling like too much energy is being put into the foam.
Landing comfort feels precise and planted, which is enabled by the extremely comfortable upper and natural position it puts your foot in. The under forefoot foam is slimmer, and the 10-millimeter heel-to-toe drop helps bring your entire foot in contact with the ground, increasing the landing comfort. Those who desire responsive cushioning should look at this model, though some may find the platform to be a bit cumbersome if you are more of a forefoot striking runner.
The thickness of the midsole foam reduces the responsiveness a bit compared to some of the other lighter-weight models. We were surprised that even with the heavier weight, the Ultraboost 21 actually does a good job of transferring power. This is partially due to the density of the foam, which isn't as soft and spongy as some other models. The heavier weight reduces the feeling of quickness and agility, but once you are planted, the firm platform helps propel you forward.
Adidas does a good job of putting most of the cushioning under the midfoot and heel, leaving the forefoot to have the ability to really transfer power. If you don't mind sacrificing a bit of weight, we think the blend of cushioning and responsiveness is suitable and won't slow you down.
The upper comfort of this model is premium and comfortable. The tight-knit elastic fabric both hugs the foot and breaths extremely well. The outer wrap helps hold your midfoot in place while the upper conforms to your foot. Some users may find the toe box a little on the smaller side but should find a perfect performance fit due to the fabric's stretchiness.
The tongue is integrated into the upper for one seamless piece of fabric, which is unlike the others we tested. The heel cup is supported by two plastic pieces which lock in the fabric and add rigidity through the heel. This is the standout feature of the Ultraboost 21, and we expect to see more upper designs like this in the future.
Lateral Stability and Support
The Ultraboost scores well for its support and stability, partially due to the well-fitting upper. The shoe feels planted and stable without feeling too rigid, and with moderate arch support, it should feel solid and predictable to most users. The forefoot is flat and allows for a natural footstrike which is supported by the 10-millimeter heel drop. Due to its higher stack height, it may feel a little less stable on uneven terrain.
The major downside of the Ultraboost 21 is its weight. At times, the model feels sluggish, especially when you feel fresh at the start of a run. Luckily this model is durable and provides many features for the added weight. The added enlarged heel ramp of the outsole offers a great platform that could help those that heel strike or need increased help getting into the toe-off position. Unfortunately, we wish these features could come in at this shoe's list price at a lower weight.
Should You Buy the Adidas Ultraboost 21?
We wish this model came in a lighter weight, but it's built with durable materials and great support, so we understand why it's one of the heavier models we tested. If you can make the price tag work and don't mind its weight, we would suggest this model for its all-around comfort. Plus, there are many colors to select from to match your running apparel.
What Other Running Shoes Should You Consider?
Everyone has different running goals. But, if you've got a need for speed, a lightweight shoe will be your best bet to smash personal record running times. Weighing in at one of the lowest weights is the Saucony Kinvara 12. At 7.7 oz, this contender is incredibly light compared to others, and it's fast and responsive. It felt like a dream on our feet during high turnover and quicker paces.
— Matthew Richardson
Ad-free. Influence-free. Powered by Testing.
GearLab is founded on the principle of honest, objective, reviews. Our experts test thousands of products each year using thoughtful test plans that bring out key performance differences between competing products. And, to assure complete independence, we buy all the products we test ourselves. No cherry-picked units sent by manufacturers. No sponsored content. No ads. Just real, honest, side-by-side testing and comparison.Learn More