Step 1

Take a thin thread or strip of paper.
Wrap the thread or paper around your finger.
Mark the meeting spot of the thread/paper end.

Step 2

Measure the length of the thread/paper in an scale.
Use the following chart to determine your ring size.
 Ring Size (Indian) Circumference
5 44.9 mm
6 45.9 mm
7 47.1 mm
8 48.1 mm
9 49.0 mm
10 50.0 mm
11 50.9 mm
12 51.8 mm
13 52.8 mm
14 54.0 mm
15 55.0 mm
16 55.9 mm
17
56.9 mm
18 57.8 mm
19 59.1 mm
20 60.0 mm
21 60.9 mm
22 61.9 mm
23 62.8 mm
24 63.8 mm
25 64.7 mm
26 66.0 mm
27 66.9 mm