are nike and under armour shoes the same size

You’ve probably been there. You’re browsing online for a new pair of sneakers, and you spot a killer deal on a pair of Under Armour shoes. You wear a size 10 in Nike, so you confidently click “Add to Cart” in a size 10 for the Under Armours. A few days later, the box arrives, you tear it open, and… your foot feels like it’s being squeezed into a sardine can. Or worse, your heel slips out with every step. The frustration is real, and it’s a classic problem in the athletic footwear world: sizing inconsistency between brands. So, are Nike and Under Armour shoes the same size? The short answer is no, not really. But the longer, more helpful answer is that understanding the “why” behind the difference can save you a lot of returns, headaches, and wasted shipping costs.

The Core Problem: Sizing Is Not an Exact Science

First, let’s clear up a common misconception. Shoe sizes, even within the same country (like US men’s or women’s sizes), are not standardized across manufacturers. Think of it like this: a “medium” t-shirt from one brand might fit you perfectly, while a “medium” from another brand feels like a tent. Shoes are the same. Nike and Under Armour are two distinct companies with their own design philosophies, target audiences, and—crucially—their own “lasts.” A last is the three-dimensional mold that a shoe is built around. It determines the shape of the toe box, the width through the midfoot, and the curve of the heel. Nike and Under Armour use different lasts, which means their size 10s are built on different foot shapes.

Generally speaking, Nike shoes tend to run slightly narrow, especially in performance models like the Pegasus or Metcon. They are designed for a snug, performance-oriented fit that locks the foot down during dynamic movements. Under Armour, on the other hand, often leans toward a roomier fit, particularly in the toe box. Their shoes, like the Charged Assert or HOVR series, are built to accommodate a wider range of foot shapes, including those with slightly wider feet. This doesn’t mean one is better than the other—it just means they’re different. So, if you have a narrow foot, a Nike 10 might feel perfect, while an Under Armour 10 could feel loose and sloppy. Conversely, if you have a wider foot, the Under Armour 10 might be your Goldilocks, while the Nike 10 could feel like a vice.

Digging Deeper: How to Compare Fit Across Brands

Instead of relying on a simple size conversion, you need to think about fit in terms of length, width, and volume. Let’s break down each aspect.

• Length: In most cases, the actual length of a size 10 from Nike and Under Armour is very similar. Both brands generally follow standard US sizing for foot length. The issue rarely lies in whether the shoe is too long or too short by a full size. It’s usually about how that length is distributed. A Nike shoe might have a slightly shorter toe box, making your toes feel cramped even if the heel-to-toe length is correct. Under Armour often provides more toe room, so you might not feel the end of the shoe as quickly.
• Width: This is the biggest differentiator. Nike’s standard D width (for men) is often perceived as closer to a C or narrow D. Under Armour’s standard D width is generally more generous, closer to a true D or even a wide D. If you’re used to Nike’s snug fit, stepping into Under Armour can feel like you’re swimming in extra space. Conversely, if you’ve always found Nike too tight, Under Armour might feel like a revelation.
• Volume: This refers to the overall depth of the shoe—how much space there is over the top of your foot (the instep) and around the sides. Nike shoes often have lower volume, meaning they sit closer to the foot. Under Armour shoes tend to have higher volume, which can be great for people with high arches or thicker feet, but it can also lead to a feeling of looseness for those with lower-volume feet.

So, how do you practically apply this? The golden rule is: Never assume a size transfer directly. If you’re a solid size 10 in Nike, you will likely need to go down half a size in Under Armour for a similar snug performance fit. But if you prefer a more relaxed, casual fit, you might stick with the same size. The best approach is to measure your foot length in centimeters or inches and compare it to the brand’s specific size chart. Even then, the chart is a starting point, not a guarantee.

Practical Tips for Buying Nike and Under Armour Shoes

Now that you know the core differences, here’s how to navigate buying shoes from both brands without the guesswork.

• Know your foot type. Are your feet narrow, medium, or wide? Do you have a high instep or flat arches? If you have narrow feet, stick with Nike or size down in Under Armour. If you have wide feet, Under Armour is likely your friend, and you might need to size up half a size in Nike.
• Read the reviews—specifically. Don’t just look at the star rating. Look for comments from people who mention their foot shape. Phrases like “I have wide feet and these fit perfectly” or “These run narrow, so I sized up” are gold. Pay attention to reviews that compare the shoe to other brands you know.
• Consider the shoe’s intended use. A running shoe from Nike (like the Invincible) might have a different fit than a training shoe (like the Metcon). The same goes for Under Armour—the HOVR running series fits differently than the Project Rock training shoes. Performance shoes are often more snug than lifestyle shoes. Always check the product description for fit notes.
• Use the “thumb test” when trying on. If you’re in a store, put the shoe on and lace it up. Press your thumb down at the end of the shoe (the toe box). You should have about a thumb’s width of space between your longest toe and the end of the shoe. If you have less, it’s too small. If you have more, it’s too big. This works regardless of brand.
• Order from a place with free returns. This is the ultimate safety net. If you’re buying online, order two sizes—your usual Nike size and a half size down for Under Armour (or vice versa). Try both on at home, walk around on carpet, and return the one that doesn’t fit. It’s a bit of a hassle, but it’s far better than getting stuck with a shoe that hurts your feet.
• Don’t forget about socks. The thickness of your socks can change the fit dramatically. If you wear thick running socks with Under Armour shoes, the roomy fit might become perfect. If you wear thin no-show socks with Nike, the narrow fit might be tolerable. Always try on shoes with the socks you plan to wear during your activity.

Final Recommendations: A Buying Strategy

So, what’s the bottom line? If you’re a loyal Nike fan looking to try Under Armour, don’t just grab your usual size. Start by going down half a size for a performance fit, or stick with your regular size if you want a more relaxed, casual feel. If you’re an Under Armour fan trying Nike, be prepared to go up half a size, especially if you have wider feet. And if you’re somewhere in between, treat each purchase as a new adventure. Measure your foot, read the reviews, and don’t be afraid to return a pair that doesn’t work.

The truth is, shoe sizing between Nike and Under Armour isn’t a simple one-to-one conversion. It’s a relationship that depends on your unique foot shape, your activity, and your personal preference for fit. But by understanding the principles of length, width, and volume, and by using the practical tips above, you can confidently navigate both brands. Your feet deserve a shoe that feels like it was made for them—not one that forces you to compromise. So next time you’re shopping, remember: size is just a number. Fit is the real deal.