To determine your ring size, you can use the following methods:

1. Measure your finger: Use a strip of paper or a measuring tape to wrap around the base of your finger and mark the point where the end meets. Then, measure the length and match it to a ring size chart to find your size.

2. Use a ring you own: Find a ring that fits comfortably on the finger you want to wear the new ring and measure the inside diameter or circumference. Then match it to a ring size chart.

3. Visit a jewelry store: Most jewelry stores offer ring sizing services and will be able to size your finger accurately.

It's important to note that finger size can change throughout the day and can be affected by temperature, humidity, and physical activity. It's best to measure your finger at the end of the day and when it's at a normal temperature.