First, don't measure your feet in the morning; feet often swell during the day due to heat and activity. For the best fit, measure your feet at the end of the day.
To measure your shoe size follow these instructions:
HEEL-TOE LENGTH
Place a piece of paper on the floor with one end against a wall. Stand on the piece of paper with your heel against the wall. Mark the piece of paper where your toes end with a pencil.
Measure from the end of the piece of paper to the mark you created with your pencil and compare the measurement to our sizing chart.
Choose the right size
That's easier said then done. Because, what do you do if you are in between two sizes?
In this case it might be safest to go for the size up, rather than the size down. And you know what? You can just try them on at home.