Buying a ring online without knowing your size is the most common source of jewelry regret. The good news: getting an accurate measurement at home is straightforward with the right approach. The bad news: most online guides skip the details that actually matter — like time of day, temperature, and what to do when you're between sizes.
Here are five reliable methods, with the trade-offs of each.
Before you start: Measure at the end of the day when fingers are at their largest. Morning measurements can run half a size small. Avoid measuring right after exercise, when hands are swollen. Cold temperatures shrink fingers by up to a half size. Repeat the measurement twice to confirm.
Method 1: String or Paper Strip (Most Accessible)
What you need: A strip of paper or thin string, a ruler
Wrap the paper or string snugly around the base of the finger you're measuring — snug, but not so tight it changes color. Mark where it overlaps with a pen. Measure the length of that strip in millimeters. That's your finger circumference. Use the size chart below to find your ring size. This method is accurate to within 0.5 sizes when done carefully.
Method 2: Measure an Existing Ring
What you need: A ring that fits the same finger, a ruler
Place the ring on a ruler and measure the inner diameter — the inside edge to the inside edge — in millimeters. Use the conversion chart below. This method is highly accurate if the ring fits correctly. If you're measuring for a surprise purchase, try to borrow a ring the recipient wears on the correct finger without being noticed.
Method 3: Downloadable Ring Sizer
What you need: A printer, scissors
Many jewelers offer printable ring sizers — a sheet with circles at each size. Print at 100% scale (no "fit to page"), cut out the circles, and hold them against an existing ring to match the diameter. Verify your printer hasn't scaled the image by checking the measurement on the guide against a ruler. Scaling errors are the most common failure mode of this method.
Method 4: Ring Sizer App
What you need: A smartphone with a calibrated screen
Several apps let you hold an existing ring against the screen to match the diameter to a displayed circle. Accuracy depends on screen calibration. Works well as a quick secondary check, but don't rely on it as your only measurement. Confirm with the string method.
Method 5: Visit a Local Jeweler
What you need: A local jewelry store
The most accurate method. A professional mandrel gives a precise measurement in seconds. Most jewelry stores will size your finger for free — it's a standard service. If you're buying an engagement ring and want to keep it a surprise, ask a friend of the recipient to visit the jeweler as a proxy, or have them measured under another pretext. Jewelers are very accustomed to this request.
US Ring Size Chart
| US Size | Inner Diameter (mm) | Circumference (mm) | UK Size |
|---|---|---|---|
| 4 | 14.9 | 46.8 | H |
| 4.5 | 15.3 | 48.0 | I |
| 5 | 15.7 | 49.3 | J½ |
| 5.5 | 16.1 | 50.6 | K½ |
| 6 | 16.5 | 51.9 | L½ |
| 6.5 | 16.9 | 53.1 | M½ |
| 7 | 17.3 | 54.4 | N½ |
| 7.5 | 17.7 | 55.7 | O½ |
| 8 | 18.2 | 57.2 | P½ |
| 8.5 | 18.6 | 58.5 | Q½ |
| 9 | 19.0 | 59.7 | R½ |
| 9.5 | 19.4 | 61.0 | S½ |
| 10 | 19.8 | 62.2 | T½ |
When You're Between Sizes
Go up. A slightly loose ring is manageable — a sizing insert (a thin plastic or metal insert added inside the band) can tighten a ring by up to half a size for $10–$20. A ring that's too tight is both uncomfortable and potentially dangerous — swollen fingers won't release a tight ring.
Exception: wide bands (8mm+) fit tighter than narrow bands of the same inner diameter. Order a half-size up for wide bands. Your jeweler can confirm this when you're specifying a wide-band design.
Ring Sizing Tips for Online Purchases
- Always confirm the seller's size guide. US, UK, and EU sizes are different. Ask for inner diameter in mm if in doubt.
- Check the return/resize policy. Any reputable jewelry seller offers at least 30 days return and should be willing to resize if needed.
- Measure the specific finger. Ring sizes vary between fingers and hands. Your left ring finger and right ring finger are often different sizes.
- Take 3 measurements over 3 days. Finger size fluctuates with diet, hydration, and temperature. Three measurements give you a reliable average.
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Browse RingsFrequently Asked Questions
What time of day should I measure my ring size?
Measure at the end of the day when fingers are at their largest. Morning measurements can be up to half a size smaller than evening measurements. Avoid measuring right after exercise or when hands are very cold.
What is the average ring size for a woman?
The average ring size for adult women in the US is size 7 (approximately 54mm circumference). Most women fall between sizes 5 and 9. Finger size varies significantly by height, build, and genetics.
Can rings be resized?
Most rings can be resized 1–2 sizes up or down. Sizing up is generally easier than sizing down. Eternity bands with stones around the entire circumference are difficult to resize. Tungsten and titanium rings cannot be resized.
What if I'm between ring sizes?
Go up. A slightly loose ring can be fitted with a sizing insert. A ring that's too tight can damage circulation and become painful or dangerous to remove.
Do ring sizes differ between countries?
Yes. The US uses a numeric scale (1–13). The UK uses letters (A–Z). Europe uses circumference in millimeters. When buying internationally, ask for the inner diameter in millimeters — this is universal.