Method 1: Measure A Ring She Wears Now
Secretly “borrow” and measure a ring that fits her left-hand ring finger (or the finger you intend her to use). Tread carefully. You don’t want her to find out! Depending on how much time you’ll have with the ring before she notices it’s gone, here are a few tactics to consider:
1. Take it to a jeweler. If you have a few hours, take the ring to a local jeweler to size it professionally. While this takes more time, it’s also more accurate.
2. Invest in a ring mandrel like this one to quickly and accurately measure the ring yourself. Slide the ring down the mandrel. The line where the ring stops indicate the ring size.
3. Use the ring sizing chart. Be sure to print it ahead of time and use a ruler to double-check it’s precisely to scale. Move the ring from circle to circle until you find the best match for the ring’s inner diameter. If the ring lands between two sizes, always choose the larger one.
4. Trace it. Carefully trace the inside and outside of the ring on a piece of paper. Repeat several times for added accuracy. Take the paper to a jeweler for a size estimate.
5. Try it on yourself. If pressed for time, try the ring on your own fingers and see if one of them fits well. If it does, you can measure that finger later, on your own time.