Quick answer: A flexible tape measure is the quickest way: wrap it snugly around the base of your finger, read where it overlaps in millimeters, and match that circumference to a ring size chart. A rigid ruler can’t wrap around a finger, so pair it with a strip of string or paper, or use it to measure across a ring you already own.
What You Need
- A flexible tape measure, such as a sewing or tailor’s tape, with millimeter markings. A fabric or plastic tape works best.
- Or: a ruler with millimeters, plus a piece of string, dental floss, or a thin strip of paper.
- A pen to mark the overlap.
- A ring size chart in millimeters, such as our cm and inch chart or our US ring size chart.
Method 1: Measure Your Finger with a Flexible Tape Measure
- Start with the tape at its zero end, and wrap it snugly around the base of the finger you’ll wear the ring on.
- Snug means it touches all the way around without pinching or leaving a mark. You should be able to slide it a little.
- Note the number where the tape overlaps itself. Read it in millimeters if you can; otherwise use centimeters or inches.
- Check that the tape sits flat and isn’t twisted, then take the reading again.
- Match the circumference to a ring size chart.
Tiffany & Co.’s own size guide describes the same method: wrap a flexible tape or string around the finger, measure the length, and compare it to the chart. Their advice if you land between sizes is to choose the larger one.
Method 2: Ruler Plus String or Paper (a DIY Ring Sizer)
If you don’t have a flexible tape, a ruler still works. This is also how to make your own ring sizer at home.
- Cut a thin strip of paper about 1 cm wide and 15 cm long, or use a length of string or dental floss. Thin paper is better than cardstock, which can add thickness.
- Wrap it around the base of your finger so the ends overlap, and mark the overlap with a pen.
- Unwrap it and lay it flat against the ruler. Measure from the end to your mark in millimeters.
- That length is your finger’s circumference. Match it to the chart.
If you’d rather not make your own, our printable ring sizer gives you a ready-made strip marked at real millimeter positions, with a 30 mm calibration line to check your printer.
Method 3: Ruler Plus a Ring You Already Own
A ruler is more useful here than anywhere else. If you have a ring that fits the right finger well, you can measure it directly.
- Lay the ring flat next to the ruler.
- Measure straight across the inside, from one inside edge to the other, at the widest point. Don’t include the metal.
- That’s the inside diameter. Match it to the diameter column of the chart.
Our existing-ring tool converts the diameter for you.
Can You Use an Online or On-Screen Ruler?
Be careful. An on-screen ruler is only accurate if the screen is calibrated, and screen size, zoom level, and browser all change how big a millimeter looks. A printed ruler is safer, but only if it printed at 100% scale. That’s why a good printable sizer includes a calibration line you can check with a real ruler. If it doesn’t measure exactly what it says, the rest won’t either.
Converting Your Reading to a Ring Size
Here are a few common readings and the US size each one matches:
| Your reading | US size |
| 50.6 mm | 5.06 cm | 1.99 in | 5.5 |
| 51.9 mm | 5.19 cm | 2.04 in | 6 |
| 54.4 mm | 5.44 cm | 2.14 in | 7 |
| 57.0 mm | 5.70 cm | 2.24 in | 8 |
| 59.5 mm | 5.95 cm | 2.34 in | 9 |
| 62.1 mm | 6.21 cm | 2.44 in | 10 |
For the full table, see our ring size chart in cm and inches. If your tape only shows inches, multiply by 25.4 to get millimeters.
Common Mistakes
- Using a stretchy tape. It reads too small once you pull it snug. Use fabric or plastic, and check it hasn’t stretched with age.
- Mixing up circumference and diameter. Around the finger is circumference. Across a ring is diameter. They use different columns.
- Pulling it too tight. A tight reading gives a size that won’t fit comfortably.
- Measuring at the wrong time. Cold hands read small, and morning fingers are smaller than evening ones. See our guide to how temperature affects finger size.
- Ignoring the knuckle. If your knuckle is much bigger than the base of your finger, the ring has to clear it. Measure both and choose a size in between, leaning toward the knuckle.
- Rounding down. When you’re between sizes, go up.
How Accurate Is a Tape Measure or Ruler?
It’s a good estimate, usually close enough for everyday rings, but it’s not a jeweler’s gauge. For an engagement ring or anything hard to resize, confirm the size with a jeweler’s metal gauge. If a ring is hard to resize, such as tungsten or titanium, see our resizing guide before you buy. For the full overview of every method, read our complete measuring guide. Wide bands fit tighter; see our wide band sizing guide.
Frequently Asked Questions
Can I measure ring size with a regular ruler?
Not around your finger, since a ruler is rigid. Use it with a strip of string or paper, or to measure the inside diameter of a ring you already own.
What kind of tape measure is best for ring size?
A thin, flexible fabric or plastic tape with millimeter markings. Avoid stretchy tapes and rigid metal ones.
What if my tape measure only shows inches?
Multiply the reading by 25.4 to get millimeters, then match it to the chart. For example, 2.14 inches is 54.4 mm, a US 7.
How do I make my own ring sizer?
Cut a strip of thin paper about 1 cm wide, wrap it around your finger, mark the overlap, and measure that length against a ruler. Or print our calibrated sizer.
Is the knuckle or the base of the finger the right place to measure?
Measure the base, where the ring will sit, and check the knuckle too. If the knuckle is larger, pick a size in between so the ring can pass over it.
