1. Take a length of floss or string and wrap it around the base of your finger.
2. Mark where the floss or string first overlaps with a pen.
3. Stretch the length of string out along a ruler or measuring tape, and take down the length in millimeters.
4. Use the ring size chart below to compare your measurement to the standard ring sizes, which go up by 0.4 millimeters every half-size. For instance, a size 3 ring is 14 mm, a size 3.5 ring is 14.4 mm, and a size 4 is 14.8mm. The most common ring sizes for women are 6 (16.5 mm), 6.5 (16.9mm), and 7 (17.3 mm), while the most common men’s sizes are 10 (19.8mm), 10.5 (20.2 mm), and 11 (20.6 mm).

Pro Tip: String and floss can stretch, so don’t pull them too taut. If you do, your measured ring finger size may be larger than your finger and any rings you purchase may be too big.