1- Position a flexible measuring tape just above your right or left ear.

2- Hold the tape with one hand and pass it over your head, allowing the tape to mold around your ears, forehead, and nape.

3- Take the tape from the top of your head (also known as the crown) to your nape. This measurement will be the height of your hat. For example, a small hat measuring 52cm would typically have a height of around 17cm.

4- Position the measuring tape at the top of your forehead and take it to the point where you want your hat to end. For example, if a hat has a 5cm brim, your measurement will include an additional 5cm.

5- Add a half-centimeter margin to each measurement taken to ensure an accurate fit. For example, a small hat measuring 52cm will have a pattern size of 52.5cm for a precise fit.