Measure more than once.
Temperature and activity affect your fingers. Repeat at a comfortable room temperature, on the finger and hand you’ll wear the ring on.
How to measure your ring size
Start with a ring that fits, or a narrow strip of paper and a ruler. Repeat the measurement before choosing a size.
Measure a ring you already wear
Choose a round ring that fits the same finger and hand. You’ll measure the space inside it, excluding the metal band.
- Open the existing-ring calculator and calibrate your screen with a standard bank card.
- Place your ring lightly against the circle. Adjust until the circle matches its inside edge.
- Check the result against your jeweler’s size chart. If you use a physical ruler instead, enter the inside diameter in millimeters.
Measure your finger with a paper strip
This method measures circumference: the distance all the way around your finger.
1 Wrap the paper
Wrap a narrow, non-stretch strip around your finger. Keep it snug without squeezing, and check that it passes your knuckle.
2 Mark and measure
Mark where the starting edge overlaps. Lay the strip flat and measure from that edge to your mark with a physical ruler.
3 Enter the length
Enter your measured circumference in the finger calculator and select the matching unit. Repeat the measurement to check your result.
Convert a size you know
Select the country or sizing system and the size printed on your ring or provided by the seller. The converter shows the closest size in each supported system.
These are approximate equivalents. Brands may use different conventions, so check the seller’s chart before ordering. Smart rings need their manufacturer’s model-specific sizing kit.
Open the size converter →Prefer to measure on paper?
Print ring circles and a measuring strip. Check the 50 mm scale line before using them.
Getting a comfortable fit
Think about the whole fit.
Your knuckle, band width, and preferred comfort matter. Between sizes? Compare the neighbors and ask your jeweler, rather than automatically sizing up.
Know when to get a fitting.
Use a professional fitting for an expensive or non-resizable ring. For Oura and other smart rings, use the exact model’s sizing kit.
Common questions
More about measurement, sizing, and calibration.
How accurate is a ring size calculator?
It gives you an estimate, not a guaranteed fit. Screen calibration, how carefully you match the inside edge, and the reference chart all affect the result. Confirm the fit with your jeweler before ordering.
Can I measure my ring size on my phone?
Yes. First match a standard bank card to the calibration outline, then place a fitting ring against the circle. Be gentle with your screen. Recalibrate after changing zoom, orientation, or devices.
What is the difference between diameter and circumference?
Diameter is a straight line across the inside of a ring. Circumference is the full distance around it. Circumference equals diameter multiplied by π. Finger width on a screen does not give a reliable circumference.
Are ring sizes the same for men and women?
The sizing systems are the same. Measure the actual finger and ring rather than selecting a size from a gender-based average.
Why do international conversion charts disagree?
Regional and brand conventions differ, and published measurements are rounded. We name our references, convert through diameter, and mark international results as approximate. The seller’s own chart takes priority.
Can I use this for an Oura or another smart ring?
Use the manufacturer’s sizing kit for the exact model. Smart-ring labels and sensor fit are not interchangeable with standard jewelry sizes.
Why did my saved calibration need checking again?
Browser zoom, display scaling, another monitor, or device orientation can change physical scale. We watch for detectable changes, but a monitor swap may look identical to a browser. Verify again whenever your setup changes.