You should choose the usual size.

However, if you have a doubt :

  1. Place a sheet of A4 paper on the floor with the edge against a wall.
  2. You or your child should stand on this sheet of paper in your bare feet, with your heels against the wall.
  3. Make sure that your heels are in contact with the wall and that your feet are flat on the floor.
  4. Draw a line on the sheet at the end of your toes.
  5. Measure the distance between the edge of the sheet and the line you have just drawn (in centimetres).
  6. Enter this measurement into the box below and your size will be displayed automatically!