Ring Size Guide
Getting your size right matters. A ring made to the wrong size is a ring that does not feel like yours. This guide gives you three ways to measure, a complete UK–US–EU conversion table, and our promise: if the size is off, we will resize it free within 30 days of delivery.
Method 1: Measure an Existing Ring
The most reliable method, if you already wear a ring on the same finger.
What you need: A ruler with millimetre markings.
Steps:
- Place the ring flat on a white surface.
- Measure the internal diameter — the distance across the inside of the band, from inner edge to inner edge. Not the outer edge. The inside.
- Record the measurement in millimetres.
- Find your diameter in the conversion table below.
The calculation: If you prefer to work from circumference: circumference (mm) = diameter (mm) × π (3.14159). Example: an internal diameter of 17.2 mm gives a circumference of approximately 54.0 mm, which corresponds to UK size N.
Method 2: Measure Your Finger With String or Floss
Use this method when you do not have a ring to measure from.
What you need: A strip of non-stretchy paper, thin string, or dental floss — and a ruler.
Steps:
- Cut a strip of paper approximately 10 mm wide and 100 mm long. String or floss also works.
- Wrap it snugly around the base of the finger you intend to wear the ring on. Snug means comfortable — not tight.
- Mark the point where the strip or string overlaps itself, using a pen.
- Lay the strip flat and measure from the end to your mark. This is your circumference in millimetres.
- Find your circumference in the conversion table below.
Notes:
- If your measurement falls between two sizes, choose the larger one.
- Measure more than once. Fingers change throughout the day.
Method 3: Request Our Printable Ring Sizer
Our printable ring sizer is a paper strip pre-marked with a sizing tab and measurement scale. It takes one sheet of A4 paper and two minutes.
How it works:
- Print the sizer at 100% scale — do not scale to fit. The accuracy depends on the print being true to size.
- To verify your printer has not rescaled: the 50 mm reference line on the page should measure exactly 50 mm with a ruler.
- Cut along the marked lines to release the strip.
- Wrap the strip around the base of your finger, threading the pointed end through the small slot.
- Pull gently until the strip sits comfortably — not loose, not biting.
- Read the UK size indicated at the slot.
Contact us at hello@monserment.com or via WhatsApp and we will send you the PDF.
UK / US / EU / Diameter / Circumference Conversion Table
| UK Size | US Size | EU Size | Internal Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|
| J | 4.75 | 49 | 15.6 | 49.0 |
| J½ | 5.00 | 50 | 15.9 | 49.9 |
| K | 5.25 | 51 | 16.2 | 50.9 |
| K½ | 5.50 | 51 | 16.3 | 51.2 |
| L | 5.75 | 52 | 16.5 | 51.8 |
| L½ | 6.00 | 53 | 16.7 | 52.5 |
| M | 6.25 | 53 | 16.9 | 53.1 |
| M½ | 6.50 | 54 | 17.2 | 54.0 |
| N | 6.75 | 54 | 17.2 | 54.0 |
| N½ | 7.00 | 55 | 17.5 | 54.9 |
| O | 7.25 | 56 | 17.8 | 55.9 |
| O½ | 7.50 | 56 | 17.9 | 56.2 |
| P | 7.75 | 57 | 18.1 | 56.8 |
| P½ | 8.00 | 58 | 18.4 | 57.8 |
| Q | 8.25 | 58 | 18.5 | 58.1 |
| Q½ | 8.50 | 59 | 18.7 | 58.7 |
| R | 8.75 | 60 | 19.1 | 60.0 |
| R½ | 9.00 | 60 | 19.1 | 60.0 |
| S | 9.25 | 60 | 19.3 | 60.7 |
Mon Serment’s standard range is UK J to S. Sizes outside this range are handled by our concierge — contact us before ordering.
Tips for an Accurate Measurement
Measure at the end of the day. Fingers are at their largest in the evening, after activity. A ring sized in the morning may feel tight by dinner.
Measure the hand you will wear the ring on. Most people’s dominant hand is slightly larger than their non-dominant hand. If you are unsure which hand you prefer, measure both.
Temperature matters. Fingers contract in the cold and swell in heat. If you live somewhere with notable seasonal temperature change — or if you are measuring in an unusually warm or cold room — account for it.
Account for the knuckle. If your knuckle is noticeably wider than the base of your finger, size to fit the knuckle. A ring that cannot pass the knuckle cannot be worn. A ring that fits the knuckle and feels slightly loose at the base can be adjusted.
Half sizes are available. If your measurement falls between two UK whole sizes, our concierge can make the ring to a half size. Message us before placing your order.
When in Doubt, Message Us
Ring sizing is one of the most common questions we receive. Our concierge is available via WhatsApp at +34 672 388488, seven days a week.
If you are in any doubt — about your measurement, about which method to use, or about how a particular shape sits on the hand — write to us before ordering. We would rather spend five minutes helping you get this right than resize the ring afterwards.
Our promise: If your ring arrives and the size is not right, we will resize it free of charge within 30 days of delivery. No conditions. No fee.
Engagement Ring Resizing — Frequently Asked Questions
Can all Mon Serment rings be resized?
Yes. All rings in the collection are made in solid 18ct gold and can be resized. Most styles can go up or down by two full UK sizes from the original without affecting the band profile. Rings with pavé set diamonds along the shank (such as hidden-halo styles) may have a more limited range — our team will advise at the point of resizing request.
How long does a resize take?
Resizing is carried out in our Dubai atelier. Allow 3–4 weeks from the date we receive the ring. We cover return shipping both ways for resizes within the 30-day window.
Are half sizes available at the time of ordering?
Yes. Our website lists whole UK sizes from J to S, but half sizes are available on request — before you place your order. Contact us via WhatsApp or email with your measurement and we will confirm the half size and add it to your order.
What if my size changes years after purchase?
Mon Serment rings carry lifetime servicing. Resizing after the initial 30-day window is available at a nominal charge, which covers courier costs and atelier time. Contact hello@monserment.com to arrange it.
Mon Serment — An Oath in Diamonds — monserment.com — hello@monserment.com — WhatsApp: +34 672 388488