Ring Size Chart: How to Measure Your Ring Size

Get your ring size right the first time to avoid needing a ring resized, returned, or delayed. Whether you are sizing for yourself or checking a customer's order before it goes to the bench, the two things worth measuring are the inside diameter of a ring that already fits and the circumference of the finger itself. Both are covered below, along with the full conversion chart in millimeters and inches.

How to Measure Ring Size at Home

There are five reliable ways to find a ring size without a jeweler present. The first two are the methods Ross Metals has always recommended, and they remain the most accurate.

Method 1: Measure a Ring You Already Own

1. Choose an existing ring that fits your desired finger.
2. Measure the internal diameter of the existing ring.
3. Match your measurement to the below chart to find your approximate ring size.

Method 2: Measure Your Finger

1. Wrap a strip of string, cord, or paper around the desired finger.
2. Make sure it is pulled very tight to your finger to ensure the best fit.
3. Measure the length of the string, cord, or paper in MM.
4. Match your measurement to the below chart to find your approximate ring size.
   

Method 3: Use a Printable Ring Sizer

A printed sizer works the same way as the string method, with the measurement already marked out for you. Print the sheet at 100 percent scale, with no page scaling or fit-to-page option selected, then check it against a ruler before you use it. A sheet printed even slightly small will read a half size out.

Ross Metals publishes a printable reference sheet that includes the ring sizing chart alongside gauge, karat and weight conversions. You can find it on the jewelry reference charts page.

Method 4: Use a Ring Mandrel or Sizing Set

A stepped mandrel and a set of sizing rings are the bench standard, and they are what a jeweler will reach for. Slide the customer's ring down the mandrel until it stops and read the size off the scale. This is the most repeatable method available and the one to use when you are sizing on behalf of someone else.

Method 5: Measure With Your Phone

Several sizing apps ask you to place a ring on the screen and scale an on-screen circle to match it. Treat the result as a starting point rather than a final answer. Screen calibration varies between devices, so confirm the reading against the chart below or against a ring that already fits before ordering.

Ring Size Chart: Diameter, Circumference and US Size

Match your measurement to the nearest value in the chart. If you fall between two sizes, take the larger one. Wide bands sit tighter than narrow ones, so for a band over roughly 6mm, going up a half size is usually the safer choice.

Tips for an Accurate Measurement

• Measure at the end of the day. Fingers are at their largest then, and a ring that only fits in the morning is a ring that comes back.
• Measure warm, not cold. Cold fingers can read a full size smaller.
• Check the knuckle, not just the base of the finger. The ring has to pass over the knuckle to get on.
• Measure the specific finger and the specific hand. The dominant hand usually runs slightly larger.
• Take three readings and use the largest. One measurement is a guess.
  

Ring Sizing for Jewelers and Resellers

If you are stocking rings rather than buying one, sizes 6 to 8 cover the bulk of women's demand and 9 to 11 the bulk of men's, which is where depth of stock matters most. Ross Metals holds finished rings, wedding bands, stackable rings and eternity bands in a full range of sizes, with no minimum order.

For custom work, ring mountings and wire rings let you set the size at the bench. If you need to convert a measurement rather than look it up, the conversion calculator handles millimeters, inches and gauge directly.

Ring Sizing FAQ

Can you determine ring size by diameter?

Yes, and it is the most reliable measurement to work from. Measure straight across the inside of the ring, edge to edge, at the widest point, then read the matching size from the chart above. Measuring the outside of the band will give you a size that is too large.

How big in diameter is a size 7 ring?

A US size 7 has an inside diameter of 17.3mm, which is a circumference of 54.4mm, or 0.68 inches across.

How do I know my ring size in mm?

Measure either the inside diameter of a ring that fits or the circumference of your finger, both in millimeters, then match the figure to the chart above. Diameter and circumference are both listed so you can use whichever you measured.

Can my phone measure my ring size?

A phone app can get you close, but screen scaling differs between devices and a mis-scaled reading is easy to miss. Use it to narrow the range, then confirm against the chart or a ring you already own.

What if I am between two ring sizes?

Go up rather than down. A ring that is marginally loose can be sized down or worn with a guard, but a ring that will not pass the knuckle cannot be worn at all.

Do wide bands need a different size?

Yes. A wide band covers more of the finger and sits tighter than a narrow one of the same size. For bands wider than about 6mm, go up a half size.

Are US and Canadian ring sizes the same?

Yes. The US and Canada use the same numeric scale, which is the scale in the chart above. UK, European and Japanese sizes use different systems and need converting.

Ross Metals has supplied jewelers, designers and retailers since 1980 from its showroom in the New York City Diamond District. If you are not sure which size to order, our team can help before you place the order. Browse the full range at Ross Metals or call the showroom.