First, let your thumb reach your little finger bottom as the picture below.
Second, use a fine line measure the hand’s most widest part as the picture below.
Third, use the ruler measure the fine line’s perimeter like the follow picture.
Fourth, convert the perimeter to the bangle size as the following conversion data.
Line Length: 6-9 cm. Bangle Inner Diameter: 4-4.5 cm
Line Length: 10-13 cm. Bangle Inner Diameter: 4.6-4.8 cm
Line Length: 13-15 cm. Bangle Inner Diameter: 4.9-5.1 cm
Line Length: 16-19 cm. Bangle Inner Diameter: 5.2-5.4 cm
Line Length: 20-22 cm. Bangle Inner Diameter: 5.5-5.7 cm
Line Length: 23-25 cm. Bangle Inner Diameter: 5.8-6.1 cm
Line Length: 26-28 cm. Bangle Inner Diameter: 6.2-6.5 cm
Lastly,just wear out jade serendipity bangle now,enjoy the bangle luster rotate like the moonshine.