Use this when you have a size in one system and need it in another — for example a South African size from a local jeweller and a US size from an online listing.
Sizing
Ring Size Converter
Ring size systems do not map onto each other cleanly. This converter shows the nearest equivalent in each system and, more usefully, tells you when the difference is large enough to matter.
Conversions are approximate. Finger size changes with temperature, time of day and the width of the band, so a converted size is a starting point for fitting rather than a final answer.
How to use it
- Choose the system your known size is in.
- Enter the size exactly as it was given to you, including any half sizes.
- Read the nearest equivalent in the other systems, and note the margin shown.
- If the margin spans two sizes, get the finger measured before ordering.
Before relying on the result
- Wide bands fit more tightly than narrow ones at the same nominal size.
- Fingers can change by half a size or more between a cold morning and a warm evening.
- Some systems use letters and some numbers, and the increments differ, so exact equivalence is not always possible.
How the tool works
The converter maps each system onto internal circumference in millimetres, then finds the nearest published size in the target system and reports how far off it is.
Data & methodology
- Data version
- PLACEHOLDER v0
- Conversion data status
- Active
- Last reviewed
- July 14, 2026
- Status last refreshed
- July 14, 2026
Methodology
PLACEHOLDER METHODOLOGY — replace with the real source of the conversion table and the date it was checked.
Frequently asked questions
Which system does South Africa use?
South Africa uses the same alphabetical system as the UK, so a South African size and a UK size are normally interchangeable. The US system is numeric and does not align, which is where most ordering mistakes happen.
Can I measure a finger with string?
You can get close, but string stretches and tends to give a size that is too small. A proper sizing ring set is far more reliable, and most jewellers will size a finger without obligation.
Should I size up for a wide band?
Usually yes, by about a quarter to a half size. A wide band sits against more of the finger and grips more, so a size that is comfortable in a 2 mm band can feel tight in a 6 mm one. Try the actual width before deciding.