“I got my running shoes about six months ago and I run about three times a week. When should I replace them?”

Your running shoes lose shock absorption, cushioning and stability over time. Running in worn-out running shoes increases the stress and impact on your legs and joints, which can lead to overuse injuries. One of the easiest things you can do to prevent those types of injuries is to replace your running shoes when they’re worn-out and have lost their cushioning.

So how do you know when it’s time to replace your running shoes? I hear that question very frequently from the runners I coach, and I follow-up with the following questions:

What’s your mileage? 

A good rule of thumb is to replace your running shoes every 350-400 miles, depending on your running style, body weight, and your usual running surface. Heavier runners may need to replace their shoes around 350 miles, while smaller runners may be able to push it past 400.

If you typically run on rough roads or trails, you’ll need to replace your shoes sooner than if you do mostly treadmill running. You should also keep in mind that you’re wearing down your shoes when you’re wearing them for things other than running, even just walking around in them. So don’t just factor in running mileage if you typically walk around in running shoes or wear them for other workouts.

It’s easy to lose track of when you bought your shoes and how much you’ve run in them. Whenever I buy a new pair of shoes, I mark the date on the inside of it so I remember when I started running in them and can estimate my mileage since then. You could also note the day you started wearing new running shoes on your training calendar or schedule.

Some runners like to rotate runners shoes or wear certain shoes for long runs, others for shorter runs or trail runs, so try to keep a rough estimate of how many miles you’re running in each. I tend to hold onto my trail running shoes for much longer than my regular running shoes because I don’t run as frequently in them.

Are you feeling any pain?

If you’ve been dealing with muscle fatigue, shin splints, or joint pain, you may be wearing shoes that have lost their cushioning. Pain on both sides — both knees, for example – is common when your shoes are at the end of their life.

Are the shoes worn-out?

The soles last longer than the shoe’s cushioning and shock absorbency, so if your soles are worn down, you definitely need new shoes. If you notice wear or holes at the front of the shoe and your shoe mileage isn’t very high, you may be wearing shoes that are too small for you. You should wear running shoes that are at least one half to a full size bigger than your street size shoes, since your feet swell as you run. Beyond wearing down your shoes, running in shoes that are too tight can also lead to issues should as blisters and black toenails.

Don’t run or workout in shoes that have worn-down soles. They probably still have some good use left in them, but save them for working in your yard or around the house. Or donate them to a local charity or organization that collects used clothing and shoes.