Why size is harder than it seems
Fingers change size throughout the day — they are larger in the evening, after meals, and during warm weather, and smaller in the morning and cold temperatures. The difference can be up to half a ring size. This means that even a professional sizing done at the wrong time of day can be slightly off.
At Jabour & Co., we include one complimentary resize within six months of delivery for precisely this reason. Getting it roughly right matters. Getting it exactly right is what the resize is for.
The most reliable at-home method
Borrow an existing ring
If your partner wears rings on the correct finger (fourth finger, left hand), borrowing one and bringing it to us is the most accurate method. We measure the inner diameter with precision gauges.
The paper strip method
Cut a strip of paper roughly 10cm long and 5mm wide. Wrap it snugly around the finger — not tight, but without gaps. Mark where the paper meets itself. Measure the length in millimetres, then divide by 3.14159 to get the inner diameter in mm. Cross-reference against the table below.
Best time to measure
Measure in the afternoon or evening, after the finger has warmed up to its typical size. Never measure first thing in the morning or when cold — the result will be too small.
UK · US · mm Conversion
Average UK women's size: L–M. If guessing, start with M.
| UK Size | US Size | Diameter (mm) |
|---|---|---|
| G | 3½ | 14.1mm |
| H | 4 | 14.5mm |
| I | 4¼ | 14.9mm |
| J | 4¾ | 15.3mm |
| K | 5¼ | 15.7mm |
| L avg | 5¾ | 16.1mm |
| M avg | 6 | 16.5mm |
| N | 6½ | 16.9mm |
| O | 7 | 17.3mm |
| P | 7¾ | 17.7mm |
| Q | 8¼ | 18.2mm |
| R | 8¾ | 18.6mm |
| S | 9¼ | 19.0mm |
| T | 9¾ | 19.4mm |
| U | 10¼ | 19.8mm |
Get sized professionally — for free
We recommend visiting us. A professional sizing with ring mandrels, at the correct time of day, and accounting for the width of your specific ring style (wider bands fit more tightly — they require a larger size) gives a result that no at-home method can match. All sizing appointments at our Hatton Garden atelier are complimentary — in person or by video, with a ring sizer posted to you anywhere in the UK.
Book a Sizing Appointment