It is important to get your ring size correct when ordering your KERV contactless payment ring. 

The best way to determine your ring size is by visiting your local friendly jeweller. If you don’t have a local jeweller, or if he or she isn’t particularly friendly, then we suggest:

  1. Download our ring size guide here (it's in PDF format) and print it off at 100%
    1. Be sure that the page prints at 100% (rather than fit to page). You can use a ruler, or a £1, €1 or 25¢ coins to check the size.
    2. The page is set at A4 size (not letter)
  2. The KERV ring size guide includes 3 separate ways to check your ring size:
    1. Ring sizer strap: a ring sizer that you cut out of the paper
    2. String: use string to measure your finger against our guide
    3. Ring comparison: measure the size of an existing ring


  • We are only accepting ring sizes in UK format i.e. letters, so if you have measured your finger in a different size format, please convert it using this chart
  • When measuring for your ring size, it’s important to do it near the end of the day, and when your fingers are warm (and therefore slightly larger). If you intend to regularly wear Kerv when performing any type of exercise, this step is even more important.
  • If using a ring sizer, ensure that it comfortably slips over your knuckle; if you have trouble getting your ring on, then you’ll have even more trouble getting it off again – especially when your finger swells up further during the struggle. We’ve all been there.
  • However, it’s also important that your Kerv ring is not so loose that it’s liable to slip off – so please measure carefully and only submit your ring size to us when you’re sure you’ve got it right!
  • If in doubt, go up a size!
  • Kerv rings cannot be resized. Sorry. Face with frown
  • Kerv rings cannot be exchanged or replaced after activation (i.e. when your payment chip is irrevocably connected to your Kerv Account) – you will have to buy a new one!

Download the KERV ring size quide (v06)

Don't forget to choose your KERV ring design