To measure your ring size at home, wrap a strip of paper or string around the base of your finger, mark where it overlaps, measure that length in millimetres, and match it to a ring size chart. That millimetre measurement is your finger’s circumference, and it maps directly to a ring size. Here’s the reliable method, the 2026 chart, and how to size a surprise ring.
I’m Suman Smith, founder of Lux Jewels. I started this as Canada’s first lab grown diamond company back in 2015, and getting the size right is the one thing people worry about most when buying online. Let’s make it simple.
Quick Answer
Wrap a strip of paper or string around the base of your finger, mark where it overlaps, and measure that length in millimetres. That’s your finger’s circumference, which maps directly to a ring size, for example about 51.9mm is a size 6 and 54.4mm is a size 7.
How to measure your ring size at home
You only need a strip of paper or a piece of string, a pen, and a ruler with millimetres. Follow these steps.
- Cut a thin strip of paper about 8cm long, or use a piece of string.
- Wrap it around the base of the finger where the ring will sit. Make it snug but not tight, and large enough to slide over the knuckle.
- Mark where the strip overlaps with a pen, making a clear single line.
- Measure the length from the start to your mark in millimetres. That number is your finger’s circumference.
- Match it to the ring size chart below to find your size.
Ring size chart (circumference to size)
Find your circumference in millimetres and read across. These are the common North American sizes.
| Circumference (mm) | US / Canada size |
|---|---|
| ~48.0mm | 4.5 |
| ~49.3mm | 5 |
| ~51.9mm | 6 |
| ~54.4mm | 7 |
| ~57.0mm | 8 |
| ~59.5mm | 9 |
| ~62.1mm | 10 |
What is the average ring size?
For women, the most common ring sizes are 6 to 6.5, and for men 9 to 10. These are useful as a fallback if you’re buying a surprise and you’ve nothing else to go on, but they’re averages, so measure whenever you can. Finger size also varies with the width of the band: a wide band fits more snugly, so you’ll want to size up a quarter to half size for bands wider than about 6mm.
How can I find her ring size without her knowing?
The easiest way is to borrow a ring she’s already wearing on the right finger and either measure its inside diameter or trace the inside circle, then bring it to us. If you can’t borrow one, lay one of her rings on the chart and match the inside edge, ask a friend or family member who might know, or note the size of a ring that fits your own finger after she’s tried it on. As a last resort, choose an average size, since most rings can be resized afterward.
Not sure of the size, or planning a surprise?
Book a private video call with Suman and we’ll help you nail the size, then design a made-to-measure certified lab grown diamond ring around it. No markup games, no sales pressure.
$199 | 30 minutes | Video call
Tips for measuring accurately
Measure at the end of the day, when fingers are at their largest, and when you’re warm, as cold shrinks fingers. Measure the same finger you’ll wear the ring on, since hands differ left to right. Take the measurement two or three times to be sure, and if you’re between sizes, go up rather than down, since a slightly loose ring’s easier to fix than one that won’t pass the knuckle. Avoid measuring with string that stretches.
What if the ring still doesn’t fit?
It’s not a problem. Most rings can be resized up or down by a size or two, and because we make every piece to order, we set your ring to your exact size from the start. If a finger changes over time, we can adjust the fit later. Getting the size right matters, but it’s never the dealbreaker people fear, and there’s always a fix if you’re slightly off.
Frequently asked questions
How can I measure my ring size at home?
Wrap a strip of paper or string around the base of your finger, mark where it overlaps, measure that length in millimetres, and match the circumference to a ring size chart. That gives your ring size accurately.
What is the average ring size for women and men?
Women most commonly wear size 6 to 6.5 and men size 9 to 10. Use these only as a fallback for a surprise; measure whenever you can for accuracy.
How do I measure ring size with string?
Wrap non-stretchy string around the base of the finger, mark the overlap, lay it flat against a millimetre ruler, and read the length. Match that circumference to a ring size chart.
How can I find her ring size secretly?
Borrow a ring she wears on the matching finger and measure its inside diameter or trace its inner circle, or lay it on a printed chart. If you cannot, choose an average size, as most rings can be resized.
Should I size up or down if I am between sizes?
Size up. A slightly loose ring can be resized down easily, while one too small may not pass the knuckle. Also size up slightly for wide bands over about 6mm.
Can a ring be resized if it doesn’t fit?
Yes, most rings can be resized up or down by a size or two. Because we make every piece to order, we set your ring to your exact size, and we can adjust it later if needed.
Related reading: lab grown engagement rings, wedding bands, and the 4Cs of diamonds.
