Is it better to get running shoes a size bigger? The truth about fit and foot space
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Based on your regular shoe size, foot width, and running distance. The article explains why proper sizing is crucial for preventing injuries and improving performance.
Ever laced up a pair of running shoes only to feel your toes jamming into the front during a long run? You’re not alone. Many runners wonder if going up a half or full size will solve the problem. The short answer? Yes-for most people, running shoes should be a half size bigger than your regular shoes. But it’s not that simple. Let’s break down why, and when this rule works-and when it doesn’t.
Why your feet swell while running
Your feet aren’t the same size at 7 a.m. as they are at 7 p.m. After 30 minutes of running, your feet can expand by up to half a size. That’s not a myth. A 2020 study from the University of Calgary tracked foot volume in 85 runners over a 10K. The average increase was 4.7%, with some runners gaining nearly a full size. That’s because blood flows into your feet during exercise, and the repeated impact causes fluid buildup. If your shoes are too tight, you’ll feel pressure on your toenails, develop black or lost nails, or even get plantar fasciitis from your foot being crushed forward.
The standard rule: Go half a size up
Most running shoe brands-including Nike, Asics, Brooks, and Hoka-recommend going up a half size from your casual shoe size. Why? Because running isn’t walking. Your foot slides forward with every stride. If your toes hit the front of the shoe, you’re not just uncomfortable-you’re risking injury. A 2023 survey of 12,000 runners by Runner’s World found that 72% of those who wore shoes at their regular size reported toe bruising or nail loss within three months. Those who went half a size up saw a 65% drop in those issues.
But here’s the catch: You don’t just need more length. You need room in the width too. A shoe that’s too long but too narrow still crushes your toes. That’s why trying shoes on in the afternoon, after a short walk or light jog, matters more than the size number on the box.
When a full size bigger might help
Not everyone needs just a half size. If you’re a long-distance runner-think marathons or ultramarathons-you might need a full size bigger. Why? Because your feet swell even more over hours of running. A 2021 study from the American College of Sports Medicine followed 67 runners during a 50K race. Foot volume increased by 8.3% on average. For runners with wide feet, flat arches, or those who run in hot climates, a full size can mean the difference between finishing strong and limping off the course.
Also, if you have bunions, hammertoes, or have had foot surgery, extra space isn’t optional-it’s necessary. A 2024 podiatry report from the Journal of Foot and Ankle Research found that 89% of runners with prior foot injuries who switched to a full size bigger reported fewer flare-ups and faster recovery times.
What happens if you go too big
Just because you need extra room doesn’t mean you should pick the biggest size available. Shoes that are too big cause other problems. Your foot slides around inside, which leads to blisters, especially on the heel and ball of the foot. You might also develop ankle instability or stress on your tendons because your foot isn’t locked in. That’s why the goal isn’t just more space-it’s controlled space.
Look for these signs you’ve gone too big:
- Your heel slips out with every step
- You feel like you’re constantly adjusting your laces
- Your toes don’t touch the front, but you still feel your foot moving side to side
- You get blisters on your heel or arch
Good fit = about a thumb’s width between your longest toe and the end of the shoe. Not less. Not more.
How to test your fit properly
Don’t just grab a size and go. Here’s how to test fit like a pro:
- Go in the afternoon. Feet are largest after a day of activity.
- Wear the socks you run in. Thick running socks change the fit.
- Stand up and press your big toe against the front. There should be a gap of about 1/2 inch (12-13 mm).
- Walk or jog in place. Your foot should stay put, not slide forward.
- Check your toes. They should be able to wiggle freely without being squished.
Pro tip: If you have one foot bigger than the other (which most people do), size for your larger foot. Don’t compromise.
Shoe width matters just as much as length
Size isn’t just about length. Width is equally critical. If you have wide feet and buy a size bigger but in a narrow width, you’re still in trouble. Brands like Altra, New Balance, and Brooks offer multiple width options (B, D, 2E, 4E). For women with wide feet, a 2E width might be the difference between comfort and pain. Don’t assume a bigger size fixes width issues-it doesn’t.
Try this: If you can pinch material on the sides of your foot when laced up, the width is too narrow. If your foot feels squeezed even with room in the toe box, you need a wider model, not a bigger size.
Brand differences matter
Not all shoes fit the same. A size 9 in Asics might be the same as a size 8.5 in Nike. Hoka tends to run long and wide, while Saucony often fits true to size. That’s why you should never rely on your size from one brand to another. Always try them on. Many running stores let you test shoes on a treadmill. Use that.
Here’s a quick guide for common brands:
| Brand | Typical Fit | Recommended Size Adjustment |
|---|---|---|
| Asics | Narrow to medium | +0.5 size |
| Nike | Narrow | +0.5 to +1 size |
| Brooks | True to size, wide options | +0.5 size if wide feet |
| Hoka | Roomy toe box, long | True to size or -0.5 |
| New Balance | Wide options available | +0.5 size for most |
| Saucony | True to size | Usually no change |
What about kids or older runners?
Kids’ feet grow fast, so it’s tempting to buy bigger. But oversized shoes hurt performance and increase fall risk. Stick to a half size max, and replace shoes every 6-8 months if they’re active. For older runners, foot shape changes with age-arches flatten, fat pads thin. Extra space helps, but support matters more. Look for shoes with firm midsoles and good heel counters, not just more length.
Final rule: Test before you buy
The best advice? Don’t guess. Go to a running specialty store. Walk, jog, and even hop in the shoes. Ask them to video your gait. Most will do it for free. Your feet are your foundation. If they’re cramped, everything else suffers-knees, hips, back. A half size bigger might feel weird at first. But after a few runs, you’ll wonder why you ever wore anything else.
Should I always go up a half size in running shoes?
For most runners, yes-a half size bigger is the standard recommendation. But it depends on your foot shape, the brand, and your running distance. If you have wide feet, a narrow shoe even a half size up might still pinch. If you’re a sprinter or do short runs, you might not need extra space. Always test the fit.
Can I just wear thicker socks instead of buying a bigger size?
No. Thicker socks add bulk but don’t solve the problem of toe jamming. Your foot still slides forward during impact. You’ll end up with pressure points and blisters. The right shoe size gives you room to move. Socks should be thin, moisture-wicking, and designed for running-not just padding.
Do I need a bigger size if I run on trails?
Yes-often more than on roads. Trail running involves constant downhill sections where your foot surges forward. Many trail runners go a full size bigger to prevent toe damage on rocky terrain. Look for shoes with a rock plate and a snug heel to keep your foot locked in.
What if my heel slips in a bigger shoe?
That means the shoe is too long, not too wide. Try a shoe with a better heel counter, or use a heel lock lacing technique. Some brands offer adjustable heel cups. If slipping persists, go back a half size and focus on width instead.
How often should I replace my running shoes?
Every 300-500 miles, regardless of size. Even if they look fine, the cushioning breaks down. Worn-out shoes force your feet to work harder, which increases injury risk. If your toes are hitting the front, it might mean your shoes are worn out, not that you need a bigger size.
