When Should You Replace Your Running Shoes?

Your running shoes have an expiry date. Unlike the milk in your fridge, there's no label telling you when that is. And unlike a flat tire or a torn jacket, worn-out running shoes don't announce themselves. They just quietly stop protecting you — and by the time you notice, the damage might already be done.

Most runners replace their shoes too late. Some run them into the ground because they still "feel fine." Others have three pairs in rotation and lose track of which one has the most mileage. A few keep that old pair in the closet for years, assuming they'll be good whenever they need them.

None of this is ideal. Let's fix that.

The 600–800km Rule

The most commonly cited guideline is that running shoes last between 600 and 800 kilometers. This number comes from shoe manufacturers, sports podiatrists, and biomechanics research. Brooks, ASICS, and New Balance all recommend replacement in this range. Some lightweight racing shoes wear out closer to 400km, while heavily built trail shoes can push past 1,000km.

But here's the catch: 600–800km is a guideline, not a rule. It's a starting point. The actual lifespan of your shoes depends on a dozen factors that are unique to you — your weight, your running surface, your gait, and even the climate you run in.

The problem is that most runners don't actually know how many kilometers their current shoes have. They might remember buying them "sometime last summer," but they can't tell you if that's 300km ago or 700km ago. Without tracking, the guideline is useless.

5 Signs Your Shoes Need Replacing

Even without precise mileage data, your shoes will eventually show physical signs of wear. Here are the five most reliable indicators:

1. The midsole feels flat. Press your thumb into the midsole foam. Fresh shoes have noticeable bounce and resistance. If the foam feels dense, hard, or compressed — especially under the heel — the cushioning is spent. This is the most important sign, because midsole degradation is what leads to injuries.

2. Uneven outsole wear. Flip your shoes over. If the rubber is worn through in patches — typically under the ball of the foot or the outer heel — the shoe is no longer providing balanced support. Uneven wear also tells you something about your gait that might be worth discussing with a specialist.

3. New aches after runs. If you start experiencing shin splints, knee pain, plantar fascia discomfort, or hip tightness that wasn't there before, your shoes might be the culprit. Worn-out cushioning transfers more impact force to your joints. Many runners blame their training when they should blame their shoes.

4. Visible creasing or cracking. Deep creases in the midsole or cracks in the outsole rubber mean the materials have broken down structurally. At this point, the shoe is well past its useful life.

5. They feel different from a new pair. This is the simplest test. If you try on a fresh pair of the same model and the difference is dramatic, your old pair is done. The tricky part is that degradation happens gradually — you adapt to less cushioning without realizing it, which is exactly why this is dangerous.

What Affects Shoe Lifespan

Not all kilometers are equal. Several factors accelerate or slow down how quickly your shoes wear out:

Body weight. Heavier runners compress midsole foam faster. A 90kg runner will wear through the same shoe significantly quicker than a 60kg runner covering the same distance. This is basic physics — more force per footstrike means faster material breakdown.

Running surface. Asphalt and concrete are harder on outsoles than dirt trails or treadmill belts. Trail running with rocks and roots causes different wear patterns — more abrasion on lugs, but often less midsole compression per kilometer.

Running style. Heel strikers put more stress on the rear midsole. Forefoot strikers wear down the front faster. Overpronators compress the medial side more than neutral runners. Your personal biomechanics create a unique wear fingerprint on every pair you own.

Climate. Heat softens EVA foam, making it compress more easily during summer runs. Cold makes rubber outsoles stiffer and more prone to cracking. Wet conditions accelerate glue degradation between layers. If you run year-round in varying weather, your shoes are under constant material stress.

Rotation. This is a big one. Running in the same pair every day doesn't give the midsole foam time to decompress between runs. Rotating between 2–3 pairs allows each shoe to recover, extending the life of every pair in your collection. We'll come back to this.

The Hidden Danger: EVA Foam Aging

Here's something most runners don't know: your shoes degrade even when you're not wearing them.

The midsole foam in most running shoes is made from EVA (ethylene-vinyl acetate) or similar compounds. EVA breaks down through a process called hydrolysis — moisture in the air slowly degrades the molecular bonds in the foam. UV light accelerates this. Heat accelerates this. Simply sitting in your closet accelerates this.

Research from materials science shows that EVA foam loses a significant portion of its cushioning properties within 2 to 3 years, regardless of use. That "brand new" pair you bought on sale two years ago and never wore? It's already lost cushioning. The outsole rubber might look pristine, but the midsole has been quietly deteriorating.

This is why buying running shoes in bulk to "stock up" on a favorite model isn't always the smart move. A shoe that sits unused for 18 months before you lace it up has already burned through a chunk of its effective lifespan.

Why "Feel" Alone Isn't Enough

The most dangerous thing about shoe degradation is that it's gradual. You don't wake up one morning and suddenly feel the difference. The cushioning declines by fractions of a percent with every run. Your body adapts. Your muscles compensate. Your joints absorb slightly more impact each week — but the change is so small that you don't consciously register it.

This is called the adaptation trap. By the time the shoe "feels" wrong, you've been running in a compromised shoe for weeks or even months. The cumulative stress has already been applied to your tendons, joints, and connective tissue. For some runners, this leads to overuse injuries that could have been prevented with a timely shoe swap.

Studies in sports medicine consistently show a correlation between shoe age and injury rates. One widely cited study found that runners who replaced shoes at recommended intervals had significantly fewer lower-extremity injuries than those who ran in shoes beyond their rated lifespan.

The takeaway is simple: don't rely on how your shoes feel. Track the data instead.

The Solution: Track Your Kilometers

If the 600–800km guideline only works when you know your actual mileage, the obvious answer is to track it.

Some runners do this with spreadsheets. Others write the date on the insole with a marker. A few try to use Strava's shoe tracking feature, which lets you assign one shoe to a run.

But these approaches all have the same limitation: they're manual, easy to forget, and they only capture a fraction of the picture. Your shoes aren't the only gear that wears out on a run. Your watch battery degrades over months. Your jacket loses water resistance after dozens of uses. Your insoles compress independently of the shoe itself.

What you actually need is a system that automatically tracks every piece of gear you use for every workout — and that understands the difference between gear that wears out by distance, by sessions, or by time.

Running shoes degrade by the kilometer. Swim goggles degrade by sessions in chlorinated water. A GPS watch degrades by years of battery cycles. A smart tracking system adapts its condition calculations to the category — so "75% worn" means something specific whether you're looking at shoes, a bike helmet, or a winter jacket.

Smart Shoe Rotation: The Data-Backed Strategy

If you're serious about both performance and longevity, shoe rotation is one of the best strategies available — and the research backs it up.

A landmark 2015 study by Malisoux et al., published in the British Journal of Sports Medicine, followed 264 recreational runners over 22 weeks. The findings were striking: runners who rotated between multiple pairs of shoes had a 39% lower risk of running-related injuries compared to single-pair runners. The theory is that different shoes alter the stress distribution on your musculoskeletal system, reducing repetitive strain on any single area.

Rotation also extends shoe life. When you give EVA foam 24–48 hours to decompress between runs, it bounces back more completely. Running in the same pair daily means the foam is always in a partially compressed state, which accelerates permanent deformation.

A practical rotation might look like this:

Daily trainer (cushioned, for easy runs) — your highest-mileage shoe
Tempo/race shoe (lighter, for speed work and races) — used less frequently, wears faster per km
Trail shoe (lugged outsole, for off-road) — different surface, different wear pattern

With three pairs in rotation, each shoe lasts longer in calendar time, and your injury risk drops. But rotation only works if you actually track each pair's mileage independently. Otherwise you're just guessing which pair needs replacing — and we're back to square one.

The Bottom Line

Running shoes are the single most important piece of equipment a runner owns. They're also one of the most commonly neglected. The 600–800km guideline gives you a ballpark, but your actual replacement point depends on your weight, surface, style, climate, and rotation habits.

Don't wait for pain to tell you it's time. Don't trust how the shoe "feels" after months of gradual degradation. And don't assume that pair sitting in your closet is still good just because it looks new.

Track your kilometers. Know your gear. Replace on data, not on hope.

GearBro automatically tracks the condition of your running shoes based on actual kilometers logged through Apple Watch and HealthKit. It knows the difference between shoes that wear out by distance and gear that degrades by sessions or time — and it tells you when it's time to replace. Learn more at gearbro.app.