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How To Find Someone’s Ring Size Without Asking.

A bespoke modern non traditional engagement ring by Kate Smith Jewellery Birmingham

Choosing the right ring for your partner can feel like a military operation. You've set your budget, found a design, picked materials, and even bookmarked gemstones.

Now, there’s just one pesky detail: how on earth do you find out - or even measure - someone's ring size without them knowing?

OK, so here's where your secret mission really begins.

Over the past 20 years, I've helped countless people go full Columbo to pull off the surprise proposal - at this point, I’m the queen of the undercover finger-measuring mission.

In my latest blog, you’ll discover three genius ways to find out someone's ring size secretly - so you can surprise them with their dream ring.

How does ring sizing work in the UK?

Before we dive into your top-secret ring measuring methods, here’s a quick lowdown on UK ring sizing if you’ve never delved into this world before.

UK ring sizes are measured in letters, ranging from A - the smallest - to Z+, the largest. There are half sizes in between each letter, e.g. L½.

All ring sizes in the UK fall within this scale, whatever the gender of the person you’re buying for. Ring measurements in the UK are in millimetres.

Each of your fingers will be a different size, and your dominant hand is usually bigger*, so your fingers will tend to be a slighter larger size on the hand you write with.

*Did you manage to read that sentence without measuring your hands against each other?

What’s the average ring size?

Average ring sizes for women in the UK range from L to O.

For men, the average ring size is usually around a T

However, that’s just to give you a very generalised guide, because everyone is different - and a good jeweller can make beautiful rings to suit every occasion and customer.

Man proposing to his partner with a ring in bed

Three ways to find out someone’s finger size secretly

Right, so now we’ve covered the basics, it’s back to the operation in hand (quite literally). Here are three methods to work out your partner’s finger size without them knowing, so you can choose THE engagement ring to pull off your perfect proposal.

Method #1: Measure the size of a ring that they already wear

If your partner already wears other rings, measuring an existing ring is an excellent place to start.

Firstly, make a mental note of which hand and finger they usually wear it on.

Then, find a way to remove it from their jewellery collection when they're not wearing it without them noticing (I didn't say your finger-measuring mission was simple - you have to have your wits about you!). Once you have your stolen treasure, you can take it to a jeweller and ask them to size it. If you're from outside of the UK, give your jeweller the international ring size - we can convert it.

Alternatively, if you’re feeling up for a further challenge, you can measure their existing ring yourself at home by following these simple steps.

How to measure ring size at home from an existing ring

  1. Grab a ruler and measure the internal diameter in millimetres - do this to the nearest 0.5 mm

  2. Then, make sure you measure the width of the band - again, to the nearest 0.5mm

  3. If you can, take a picture of it, showing the shape of the band

Pass this information on to your jeweller - they will be able to work out their size from here.

How to measure a ring accurately to find out someone's finger size


Tell your jeweller which hand your partner wears the existing piece of jewellery on. As your dominant hand is usually larger, your jeweller will need to take this information into account if the engagement ring will be worn on the opposite (left) hand.

Method #2: With a little help from friends... and family

For some people, measuring an existing ring to determine finger size simply isn’t an option. Maybe your partner doesn’t really wear much jewellery, or they’re super observant and would notice you loitering by their jewellery box and smell a rat.

If that sounds like your loved one, it’s time to try Method #2: recruiting other agents to join your mission.

From my experience, there are three main ways to go about getting help from friends and family to find out your partner’s ring size.

Which one will you go for?

The casual swap

Speak to your partner’s friend, sister, brother, mum, or dad about orchestrating a situation where they casually try each other’s rings on to see what fits well on their ring finger.

If they happen to try on a friend’s ring that fits, you can go back to Method #1 and either do some DIY ring measuring or take it to a jeweller to be sized.

Or, the ring owner may already know the size of the ring, making your job even easier.

The shopping trip

You could ask friends/family to organise a shopping trip with your partner.

As they pass a jewellery shop, task them with trying on some rings and asking your partner’s opinion on them.

What happens next?

Nine times out of ten, someone in this situation won’t be able to resist trying rings on too - I’d be amazed if your partner doesn’t join in the fun!

The friend/family can casually ask the shop staff what size it was they tried on and make a mental note for you later.

2 women trying on rings together

The body double

Finally, one way of estimating your partner’s ring size with the help of their nearest and dearest is to choose someone of a similar size and physique, like a sibling or friend.

Once you’ve identified a suitable body double, you can measure their ring finger size yourself, or ask them to get it measured professionally by a jeweller.

While this may not generate an exact result, it’s better than a total guess, so you’ll either get lucky or at least get a lot closer to the correct size.

Method #3: Ask them to try a ring on

No, I haven’t lost my mind - I know it's meant to be a surprise.

The idea here is that you buy an inexpensive ring under the ruse that it's a gift for someone else, like your mum, sister, or dad.

Casually show it to your partner and ask them for their opinion.

See what they think about the style, and then throw in a passing concern over the sizing; now you’ve got it home, you’re worried it’s not going to be a good fit!

Trust me, this will magically compel them to try it on their own hand for comparison!

Just a few things to remember if you go for this undercover ring size measuring option:

  • You’ll need to have a fairly good idea of your partner’s ring size before going out to buy the decoy ring - if it’s way too big or small, this entire exercise will be pointless

  • Is a ring something you’d be likely to buy for said family member? If it’s a very out-of-character choice for you, this could raise alarm bells and blow your cover, so apply common sense

  • If you do execute this operation successfully, make sure to follow through by actually gifting the ring you said you would - otherwise, you’ll likely get busted!

newly engaged couple wearing Kate Smith Jewellery ring handmade in Jewellery Quarter Birmingham UK

What to remember if you’re guessing someone’s ring size

If it comes down to guesswork, here are some things to bear in mind…

Go big (or go home with an empty camera roll)

Many people struggle going undercover and feel like they’ll slip up and ruin their entire surprise, so if you’re still unsure about the best way for you to measure your partner’s finger size without them knowing, don’t panic.

If you’re making an educated guess on your partner’s ring size, it’s best to size up slightly - by one size.


Well, as long as the engagement ring you choose actually goes on, you can still capture those lovely engagement photos and get the ring resized later.

If it’s too small, you risk ruining that Insta moment and putting a bit of a dampener on your special day.

And remember: Resizing is always an option

Planning a proposal is an exciting time, but I know it can also be stressful and anxiety-inducing with so many variables at play. So it’s natural that you might now be thinking: “What if the ring doesn't fit after all that?”

I wanted to reassure you that an ill-fitting engagement ring is far from the end of the world - and it’s absolutely NOT a bad omen! Despite all your best efforts to decode your partner’s ring size, it’s not always possible to work it out with 100% accuracy, and many people in your shoes miss the mark.

Please don’t worry if that happens - it’s more common than you think and it can easily be rectified. Most rings can be altered slightly if the fit isn’t quite right.

In fact, we actually offer this service for free, within one finger size of adjustment either way.

Using a plastic ring sizer to find out your finger size

How to find out your own finger size

To make this easier for you, we have a free sizing gauge you can use yourself at home.

Better still, we’ll send this out to you absolutely free of charge so it’s one less thing to worry about - simply send us a message - with your address - and we’ll get one out in the post to you.

Get help choosing the perfect engagement ring

Of course, sizing is only one part of choosing the right engagement ring for your favourite person. You want a ring as special as your wonderful partner, so I know how important it is for you to get this right.

If this is causing you sleepless nights, please get in touch.

Kate Smith at her bench in Birmingham's Jewellery Quarter

My team and I have been creating beautiful, unique, and timeless engagement rings for over two decades now, so we’re experts at helping you navigate this often confusing new world so you feel confident, calm, and excited about your big moment.

Drop us a line to discuss your ideas and questions, or if you’re local to Birmingham contact us to make an appointment to come and chat at the workshop - we’d love to meet you in person.

Need some inspiration to get started now? Browse our range of contemporary engagement and eternity rings here.

A diamond and emerald non traditional engagement ring by Kate Smith Jewellery

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When I’m not at the bench creating jewellery or sitting at the laptop writing my next blog post for you, I can usually be found cuddling our fluffball of a cat, Kenji, watching Tottenham getting thrashed with my eldest son, or playing table tennis with my youngest at the kitchen table. Oh, and I happen to be married to the most supportive man, who still makes me giggle after all our years together. Yep, I lucked out there didn't I?


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Solitaire twist 0.80ct diamond gold engagmement ring by Kate Smith, Jewellery Quarter. UK.
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