At the 2021 Boston Marathon, I felt a flash of pain in my left foot. Despite the searing burn on my toes, I managed to run just two minutes shy of a sub-three-hour race. My ivory shoes were still white, save for a copper-colored streak. A friend initially thought the blotch was part of the shoe’s design. It was dried blood.
Racing in the wrong shoe size is a rite of passage for new runners and a rookie mistake for vets like me.
But hang on—I’m not the only one at fault here. As a Runner’s World gear editor, I’ve noticed fit, length, and width can vary among a single brand’s different shoe models, even when the sizes on their boxes are the same. So, what’s going on with shoe sizing?
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To find out, I spoke with runner and FleetFeet content marketing specialist Caroline Bell—a former FleetFeet sales associate, she’s worked on the retail side, too—and podiatrist and performance footwear consultant Simon Bartold.
Try This on for Size
“Sizing generally is a nightmare, with no universal system,” said Bartold, who was an Asics research consultant. He noted how the three major sizing systems—U.S., U.K., and European—are completely different. A men’s U.S. 9, for example, is a U.K. size 8 and European size 42.
“In addition, length and width basically do not talk to each other. So, going by measurement—in itself a Pandora’s box—you may be a U.S. 7, but you might need to go to a U.S. 9 or 10 to get satisfactory width fitting,” said Bartold. “Likewise, it can go the other way if one has a narrow foot. A measured U.S. 7 might need to go down to a U.S. 5 to stop slippage.”
One way to find a secure fit is to try a shoe in different widths. The standard width is D for men and B for women. Some specialty running shops carry other widths to accommodate runners who don’t fit the industry standard. FleetFeet stores, for instance, tend to carry wider EE widths for men and D widths for women, but you should call the store beforehand, said Bell, to make sure they have those or other widths in stock.
“It will vary by store, but I think finding an AA, which is a narrow size for women, might be a little bit of a challenge,” said Bell. “I would recommend calling the store because they will usually need to put in a special order for you.”
However, choices may be limited, as not all models are available in extended widths.
Sizing Isn’t Made to “Last”
Sizing is also inconsistent within a brand’s shoe collection because brands tend to use different lasts for certain models. A shoe’s last is the solid form used to develop a shoe’s shape and volume. Some brands will use lasts with a slimmer, narrower fit on their competition shoes and lasts with a wider midfoot for their more cushioned trainers.
Adding to the headache, sometimes a shoe doesn’t fit the same way as its previous version.
“This is actually something I have never understood,” said Bartold. “How a franchise, let’s take the Asics Kayano as an example, now on its 29th iteration (Bartold worked on the Kayano 8 through 20), could have a different fit to the previous models. The last is the same. The development process will be the same, so it has to have a design flaw. Weird, but it happens.”
Altra conveniently identifies each model’s last on its shoe’s webpage. The brand has three foot shapes: slim, standard, and original. The original fit has the widest width in the midfoot.
Some brands, like Altra, Asics, and Puma, also use gender-specific lasts. “There are differences morphologically and biomechanically between men and women,” said Bartold.
A woman’s last is formed to accommodate narrower heels, higher insteps, and a greater quadriceps angle. But not every woman fits this mold. Hilma, a women’s shoe startup, wants to change that by offering a shape for every kind of foot.
Personalization By Trial
“Our basic premise is mass personalization of running shoes. The way we approach that is two-fold,” said Hilma founder and CEO Brooke Torres.
The first part is completing a survey on the company website. Questions focus on preferred sizing, which brands fit you best and which fit you worst, common shoe issues (heel slippage, cramped toes, lack of support), and habitual information (“How many running shoes have you tried in the past three years?”).
Based on your answers, the site will recommend one of Hilma’s three fits and sizing. A pair is priced at $159 (free shipping included), and you can choose from three colors. Free exchanges and returns are available.
Torres fell in love with running in 2016, when she ran her first 26.2 at the Baystate Marathon in Massachusetts. Trail and ultrarunning would soon follow. As she became a more emboldened runner, she had hang-ups finding the right running shoe.
“I was reading reviews and I was going to the running store. I would order stuff online, try it at home, and need to send it back,” she said.
Torres initially thought she was an “edge case.” Discussion with other women runners made her discover she was the norm.
“I started to realize how widespread the problem was. When I found a fit that worked well for me, I would take it to other friends who were in theory the same size, but the dimensions of our feet were different,” she said.
Using her marketing consultant chops and passion for the sport, Torres began building Hilma in 2019. She assembled a product development team and had their shoes tested by a broad range of women.
The three fits have an 8mm offset and other commonalities, but if you put them side-by-side, you’ll notice that Hilma One has a narrower silhouette, Hilma Two has a curvier toebox, and Hilma Three has a wider midfoot area. The foot shapes consider the length and volume of your foot, and its quirks (e.g., bunions, a longer second toe, a higher instep).
I was able to try all three shoe forms and picked Hilma Two as the best fit. When I took the online survey, I was surprised how the site accurately chose the same pair. On the run, my Hilmas felt as supportive and responsive as a run-of-the-mill daily trainer. Torres herself ran a 30-miler in the shoes.
Hilma currently has one model, but Torres hopes to create even more layers of personalization based on runner feedback. Someday, perhaps, Hilma will create the best-fitting shoes for all women runners, allowing them to choose a shoe that truly meets the Goldilocks standard.
Crafting the Ideal Shoe(s)
Hilma founder and CEO Brooke Torres walked us through the features that all three fits share.
- Mesh Upper: “I had so many blisters when I was running. Sometimes that was a fit thing, but also sometimes it was a breathability thing. I wanted a material that was airy and comfy.”
- Sugarcane-based EVA Midsole: “From an environmental standpoint, we felt that it’s better than traditional petroleum-based EVA. We can use more environmentally friendly materials without sacrificing performance.”
- Hybrid Outsole: “We were careful to make it light enough so it didn’t feel heavy and weighed down, but gave it that little bit of extra traction so you can be spontaneous in them.”
Shoe Fitting Tips
You most likely don’t have a Brannock device or 3D foot scanner at home—and judging by my findings, you can’t rely on size alone. You have to try on the shoes. Here’s some advice on how to find the right fit.
- Use your thumb. For shoe length, we recommend using your thumb’s width to determine how much room you’ll need between the shoe’s tip and your toes. “Make sure you’re standing up,” said Bell. “When you stand and you’re bearing weight, your foot will change positions.”
- Use your fingers. One way to check whether you’re wearing the correct shoe width is to place your fingers on top of the lacing. If only one finger covers the middle of the laces, the shoe is too wide. Room for three fingers means your shoe is too narrow. Space for two fingers is just right.
- Go shoe shopping in the afternoon. “The old adage that you should buy shoes at the end of the day does hold some water,” said Bartold. Your feet swell during a run or race. Trying on shoes after you’ve been on your feet for hours is one way to simulate that.
- Get fitted at a store. Sure, we’ve given you these pointers, but your most valuable shoe-fitting asset is an actual shoe fitter. “If you can, go to a local running store and get a fitting,” said Bell. “Even if you think you know exactly what size you are, you may be surprised and learn something you didn’t know about your feet. Most stores won’t charge you.”
Amanda is a test editor at Runner’s World who has run the Boston Marathon every year since 2013; she's a former professional baker with a master’s in gastronomy and she carb-loads on snickerdoodles.
