You’ve decided on the ring. The only thing between you and ordering is a dropdown with six numbers in it, and no idea which one is yours.
How to Choose Your Tangem Ring Size
Learning how to choose your Tangem Ring size takes about five minutes and one piece of string. What follows is the method, the size range, and the two facts that settle close calls because a ring that’s slightly wrong is the one thing about this product you can’t fix with a firmware update.
The short answer
Measure the finger you’ll actually wear it on, late in the day when your fingers are at their largest, and round up if you fall between two sizes. Tangem Rings come in sizes 8 to 13 US, which corresponds to an inner diameter of roughly 18.9mm to 22.33mm.
Measure twice, on different days, before you order.
The four ways to measure, ranked
Tangem publishes four methods. They’re not equally reliable, so here they are in order of how much I’d trust the result.
Best: use a ring you already own
If you have a ring that fits the finger you’re planning to use, this removes most of the guesswork — you’re measuring a rigid object rather than soft tissue that changes size through the day.
Place the ring on Tangem’s printed sizing guide and find the circle that sits just inside the ring’s inner edge. Or measure the inner diameter directly across the widest point with a ruler, in millimetres.
One caveat covered further down: band width affects fit, so a chunky ceramic band won’t feel identical to the thin band you measured.
Good: the printable sizing guide
Tangem provides a printable guide with three tools on it a paper sizer you cut out, printed circles to match an existing ring against, and a chart for the string method.
The instruction that matters most: print at 100% with no scaling. Then verify before you trust it measure the printed ruler against a real ruler, or place a coin on the matching circle to confirm the scale came out right.
A guide printed at 94% gives you a confident, wrong answer. This is the single most common way people mis-size a ring at home.
Workable: string or paper around your finger
No printer? This works.
- Cut a strip of paper or take a length of non-stretchy thread stretchy string will read small.
- Wrap it snugly around the base of your finger. Snug, not tight.
- Check it slides over your knuckle with a little resistance if it won’t pass the knuckle, it’s too small regardless of what the base measurement says.
- Mark where it overlaps, lay it flat, measure the length in millimetres.
- Compare against the size chart.
Least reliable: apps and guessing
Phone apps that size rings from a photo, or “my mate’s ring fits me so I’ll take his size.” Fine as a sanity check against a proper measurement. Not fine as your only input on a purchase in this price range.
The size range
| Tangem Ring sizes | Inner diameter |
|---|---|
| US 8 to US 13 | approx. 18.9mm – 22.33mm |
Circumference runs roughly 59mm at the smallest to 70mm at the largest.
[PLACEHOLDER: reproduce Tangem’s current published per-size chart here — US size against exact inner diameter and circumference — and link to their official sizing PDF rather than paraphrasing. Tangem’s stated range starts at 18.9mm for size 8, which differs slightly from generic jewellery charts, so use their numbers rather than a standard conversion table.]
That last point matters. Generic ring charts and Tangem’s own chart don’t line up exactly at the small end, so size from Tangem’s figures.
The two facts that settle close calls
This is where most sizing guides stop short.
Between two sizes? Take the larger one
This is Tangem’s own guidance, and the reasoning is simple: a slightly loose ring is wearable and a slightly tight one isn’t. A tight ring gets left in a drawer, which makes it an expensive ornament.
There’s a limit, obviously loose enough to slide off in cold water is its own problem. But when you’re genuinely between 10 and 11, take 11.
There’s a manufacturing tolerance of ±0.25mm
Tangem states this openly on their size chart: the finished ring can be exactly the quoted size, or about two average human hairs larger or smaller, because of the polishing process.
Two things follow. First, measuring to a tenth of a millimetre is false precision you are working to a tolerance wider than that. Second, if your ring feels marginally different from another of the same stated size, that’s the explanation rather than a fault.
Five things that change your finger size
Fingers aren’t a fixed measurement, which is why one hurried measurement isn’t enough.
- Time of day. Fingers are smallest in the morning and largest in the evening. Measure late.
- Temperature. A frosty Central Otago morning and a humid Auckland afternoon will give you different readings on the same finger.
- Exercise and heat. Fingers swell after a run, at the gym, or on a hot day.
- Salt, alcohol and poor sleep. All cause short-term swelling.
- Which hand. Your dominant hand is usually slightly larger.
The practical response: measure two or three times across different days and times, and go with the larger consistent result.
Which finger will you wear it on?
More consequential than it sounds, and worth deciding before you measure rather than after.
Three things to weigh:
What’s already occupied. If a wedding or engagement ring has the obvious finger, you’re choosing between an adjacent one and the other hand and every finger needs its own measurement. Don’t assume.
Grip and daily use. A ring on an index finger gets involved in everything you pick up. Many people find a middle or ring finger more comfortable for something worn continuously.
The tap. You’ll be tapping your hand to your phone to sign transactions. Pick a hand and finger that makes that motion natural the hand you usually hold your phone in is often the wrong choice, since you’d be tapping a device against the hand holding it.
Band width affects fit
Underexplained everywhere, and a genuine source of sizing errors.
A wide band covers more of your finger and generally feels tighter than a thin band of the same nominal size. So if you’re sizing from a slim wedding band or a delicate fashion ring, the same number in a wider ceramic ring may feel snugger than you expect.
If you’re on the boundary and sizing from a thin ring, that’s another argument for taking the larger option.
A New Zealand note on sizing
NZ and UK jewellers use letters, not numbers. If you get measured locally, you’ll be told something like “S” or “T½” rather than a US number, and that needs converting before you order.
Rough conversions run from around UK Q/R at US 8 up to UK Z at US 13, but these vary between charts and should be checked against Tangem’s own conversion table rather than trusted from a general guide.
The two-minute shortcut: walk into any jeweller and ask them to measure your finger. Most will do it free, it takes moments, and a professional ring sizer beats every DIY method on this page. Ask for the US size, or the letter and convert it carefully.
What if it doesn’t fit?
The honest answer: ceramic can’t be resized. A metal band can be stretched or cut down by a jeweller; a zirconia ceramic ring cannot. So the remedy is an exchange, not an adjustment.
One reassurance worth stating: your wallet isn’t affected either way. The cards in the box hold the same wallet, so a ring exchange is a hardware matter rather than a crypto one.
Before you order: the checklist
- Choose the finger and the hand, thinking about the tap
- Measure late in the day, when fingers are largest
- Measure twice, on separate days
- Cross-check with a second method string plus an existing ring, ideally
- Round up if you’re between sizes
- Confirm against Tangem’s published chart, not a generic one
Five minutes, spread over two evenings. Worth it for something you’ll wear daily.
FAQs
What sizes does the Tangem Ring come in?
Sizes 8 to 13 US, corresponding to an inner diameter of roughly 18.9mm to 22.33mm. If your size falls outside that range, the card set is the option that fits everyone.
What if I’m between two sizes?
Take the larger one. That’s Tangem’s own guidance a slightly loose ring is wearable, a tight one gets left in a drawer.
Can a Tangem Ring be resized?
No. It’s zirconia ceramic, which can’t be stretched or cut down the way a metal band can. If the size is wrong, it needs exchanging rather than adjusting.
How do I measure my ring size at home?
Wrap non-stretchy thread around the base of your finger, mark the overlap, and measure the length in millimetres. Or measure the inner diameter of a ring that already fits. Check it passes your knuckle with slight resistance.
Does it matter which finger I wear it on?
Yes each finger is a different size, so measure the one you’ll actually use. Also consider which hand makes tapping your phone natural, since that’s how you’ll sign transactions.
What if I order the wrong size?
Check the exchange terms before ordering. Your wallet is unaffected either way the backup cards in the box access the same wallet, so a size problem is a hardware inconvenience rather than a crypto one.
How do New Zealand ring sizes convert to US sizes?
NZ and UK jewellers use letters. Roughly, UK Q/R corresponds to US 8 and UK Z to US 13, but conversions vary between charts check Tangem’s own table, or ask your jeweller for the US size directly.
The bottom line
Measure the right finger, late in the day, twice, with two different methods. Round up if you’re between sizes, and remember the ±0.25mm tolerance means precision beyond that is wasted effort.
And if sizing is genuinely what’s stopping you, the card set does the same job with no fit to worry about. The ring is convenience worth having, but not worth ordering a size you’re unsure of.
