In the United States, the average woman’s ring size is a . While this is a helpful starting point, finger sizes vary significantly based on height, bone structure, and even the climate. Because it is much easier for a jeweler to "size down" a ring (remove metal) than to "size up" (stretch or add metal), it is usually safer to aim slightly large if you are guessing. The "Stealth" Methods

If you want to keep the proposal a secret, you’ll need to be resourceful.

Borrow a ring your partner currently wears on their ring finger (or middle finger, which is usually a half-size larger) and trace the inside circumference on a piece of paper. A jeweler can use this circle to determine the diameter.

Fingers tend to swell throughout the day. It is best to measure in the evening when the hands are warmest.

Wider bands fit more snugly than thin bands. If you are planning on a thick, chunky setting, you may need to go up a quarter or half size. Choosing a Resizable Setting