The complete UK guide to secretly finding someone's ring size — 8 clever methods including borrowing a ring, the sleep method, hand comparison, enlisting friends, soap imprint, and what to do if you get it wrong
The most reliable way to secretly find someone's ring size is to borrow one of their existing rings — ideally one they wear on their left ring finger — and take it to a UK jeweller to be measured. If you cannot borrow the ring, tracing its inner circumference on paper and taking the tracing to a jeweller is just as effective. Do not worry too much if the size is slightly off — the most important thing is to get close, as most UK jewellers offer a free first resize after purchase.
Discreetly borrow a ring they wear on their left ring finger. Take it to a UK jeweller who can measure it instantly for free using a ring mandrel. Return it before it is missed. Choose a ring from a jewellery box they rarely check rather than a daily-wear favourite.
★★★ Most AccurateIf borrowing feels too risky, place their ring flat on paper and carefully trace around the inner circumference using a pencil (never a pen — ink can transfer to the ring). Take the paper to a UK jeweller and they will work out the exact UK size from your tracing.
★★★ Very AccurateSlide their ring onto your own finger as far as it will go and mark the point with a felt tip. Take your hand to the jeweller who can use a ring sizer to translate the mark into a UK letter size. Works even if the ring only reaches your first knuckle.
★★★ Very AccuratePress their ring firmly into a small bar of soap or soft candle wax to create a clean impression. The jeweller can measure the imprint diameter to find the UK size. Use a hotel miniature soap bar — the perfect size for a clear impression. Wipe off any residue before returning the ring.
★★ Good AccuracyWhile they are sleeping soundly, gently wrap a thin piece of string or a ring sizer around the base of their ring finger. Mark the overlap and measure the length. Works best when they are in deep sleep. Use a soft material that will not wake them — never use wire or anything rigid.
★★ Good AccuracyAsk their best friend, sister, or mother — someone who knows their ring size or can find out naturally. A friend can casually suggest trying on rings together, or ask about ring sizes as part of a jewellery conversation. Often the easiest and most reliable method of all.
★★★ Very AccurateDuring a natural hand-holding moment, compare the size of their ring finger to your own fingers. Note which of your fingers it most closely matches in width. Visit a UK jeweller with that finger and they can use a ring sizer to estimate the UK letter size.
★★ Rough EstimateAsk them casually while browsing jewellery online or in a shop together — "what size do you think you are?" Alternatively, use a costume ring or charity shop ring as a "test fit" game. Or ask a friend to mention that they need to know their own ring size and ask your partner to find out theirs at the same time.
★ Last ResortIn the UK, engagement rings and wedding bands are traditionally worn on the left ring finger — the fourth finger of the left hand. Ring sizes differ between fingers and between hands, so always try to borrow a ring they wear specifically on their left ring finger for the most accurate result.
Do not borrow a daily-wear ring they might notice is gone. Look in their jewellery box, drawer, or bathroom shelf for a ring they wear occasionally. A ring that has not been worn recently is the safest choice — they are unlikely to notice it has been briefly moved.
Walk in to any UK high street jeweller — H.Samuel, Ernest Jones, Goldsmiths, or an independent jeweller. Ask them to measure the ring's internal diameter. This takes less than 60 seconds and is done for free. They will give you the exact UK letter size. You do not need to buy anything.
Ask the jeweller to note down the UK letter size (e.g., M½) and the diameter in millimetres (e.g., 16.7mm). Having both means you can use either measurement when ordering online or from a different jeweller, and it helps avoid any sizing confusion between retailers.
The whole process should take 30–60 minutes maximum. Return the ring to exactly where you found it before they notice it is gone. If in doubt, borrow it while they are out of the house, asleep, or otherwise occupied for a reliably safe window of time.
Same principle as the borrow method — choose a ring from the correct finger for accuracy. Even an approximate match from a ring worn on their right ring finger is useful as a starting point.
Place it face-up on plain white paper on a flat, well-lit surface. Using a pencil only (never a pen or marker — ink can transfer onto the metal and give the game away), carefully trace around the inside edge of the ring band to create a clean circle.
Using a ruler, measure across the widest point of your traced circle in millimetres. This is the ring's internal diameter in MM. You can look this up in a UK ring size chart yourself, or simply take the tracing to a jeweller who will measure it professionally.
Bring the paper tracing to any UK jeweller. They will place ring sizers over the traced circle to find the matching UK letter size in seconds. This is completely free at most UK jewellers and far more accurate than relying on your own measurement alone.
Put the ring back exactly where you found it straight away. Keep the tracing somewhere safe — photograph it on your phone as a backup in case the paper is lost before your jeweller appointment.
| Method | Accuracy | Risk of Discovery | Time Needed | Best For |
|---|---|---|---|---|
| Borrow a Ring | ★★★ Highest | Medium | 30–60 mins | Engagement & wedding rings |
| Trace the Ring | ★★★ Very High | Very Low | 10–15 mins | When borrowing feels too risky |
| Mark Your Finger | ★★★ Very High | Very Low | 5 mins + jeweller visit | When ring is available briefly |
| Enlist a Friend | ★★★ High | Low–Medium | Variable | When partner is communicative |
| Soap / Wax Imprint | ★★ Good | Low–Medium | 10 mins | When ring cannot leave the house |
| Sleep Method | ★★ Good | Medium | Requires deep sleeper | Last resort if other methods fail |
| Hand Comparison | ★ Estimate Only | Very Low | Immediate | Quick ballpark for online browsing |
| Drop Hints / Game | ★ Estimate Only | High | Variable | Non-surprise purchases |
Even with the best secret methods, getting the ring size exactly right first time is not always possible. The good news is that most UK jewellers — including H.Samuel, Ernest Jones, Goldsmiths, and Beaverbrooks — offer a free first resize within 30–90 days of purchase. Always ask about the resize policy before buying. If in doubt, size up by half a UK letter — a slightly larger ring can be adjusted, and wearing a slightly loose ring temporarily is always safer than one that cannot be removed.
If you are not confident in the measurement, always buy the larger of the two sizes. A ring that is slightly large can be worn with a temporary ring guard, then resized later at no cost.
Ask your UK jeweller about their free resize policy before purchase. Most UK retailers offer at least one free resize within 60–90 days. Get this confirmed in writing or check the website before you commit.
A clear plastic ring guard costs £3–£10 online and can make a slightly large ring fit perfectly as a short-term solution while you wait to resize. Available from Amazon UK and most jewellery shops.