Correct Shoe Size

So how do you determine how your shoes should fit? Try these steps:

Step 1: Line the Insole up With Your Foot

Take the insole (or sockliner) out of the shoe and stand on it. The size and shape should match the size and shape of your foot, Vincent says. Your toes shouldn’t spill over the front or sides, and the tip should come to a point roughly where your toes narrow.

Step 2: Assess Lace Tightness

Put the insole back in and put the shoes on. Lace them tightly enough to lock the shoe over your navicular bone—the bony bump over the high point of your arch—or instep, Gray says, but not so tightly that you constrict nerves and blood vessels. You should be able to slide a finger between the knot and your shoe, Vincent says.

Step 3: Check Your Toes

Stand up and check the feel and fit. You want about a thumbnail’s worth of width between your longest toe and the front of the shoe, keeping in mind that your longest toe may be your second metatarsal (the heads of the long toe bones) and not your big toe. As for width, check that there’s little to no pressure on your pinky toe and only slight pressure on your big toe—slightly looser than the snugness of a watch strap on your wrist, Gray says.

Step 4: Walk and Run

Walk—and, preferably, run. Check that your heel doesn’t slip and that nothing pinches or rubs uncomfortably against your ankle. Also, check the fabric of the upper—if it gathers or bunches you might need a snugger fit, and if it bulges or stretches, you might need to go bigger, says Allison Bowersock, Ph.D., an exercise physiologist and co-owner of RunAbout Sports, a specialty running-shoe store in Roanoke, Virginia.

Step 5: Repeat, as Needed

Don’t settle for something cramped thinking you’ll break them in; your running shoes should fit properly right from the start, Vincent says. While some parts of the shoe—including the midsole and cushioning—may change for the better with mild wear, that doesn’t affect the sizing or fit, Gray says.