· 6 min read
How to Measure Ring Size at Home Without Guessing
How to measure ring size at home using string, paper or a ring you already own, plus the sizing mistakes jewellers see most and when to get measured.
You can measure ring size at home with a ring that already fits, a strip of paper, or a piece of string, and land within half a size of the correct answer. Measuring a ring the wearer already owns is the most accurate of the three by a wide margin. Everything below is how to do each method properly, plus the small things that quietly throw the number off.
Measure a ring that already fits
Borrow a ring the person wears on the finger you're sizing. Not a ring from another finger, not one they've outgrown. The left ring finger and the right ring finger on the same person often differ by a quarter to a half size, and the dominant hand is usually the larger of the two.
Lay the ring flat and measure the inside diameter, edge to edge across the widest point, with a ruler marked in millimetres. Do it three times and take the middle reading. A millimetre of error is roughly a full ring size, so this is worth being fussy about. If you have digital callipers in a toolbox, use them.
Reading the number
| Inside diameter | Inside circumference | North American size |
|---|---|---|
| 14.8 mm | 46.5 mm | 4 |
| 15.7 mm | 49.3 mm | 5 |
| 16.1 mm | 50.6 mm | 5.5 |
| 16.5 mm | 51.9 mm | 6 |
| 16.9 mm | 53.1 mm | 6.5 |
| 17.3 mm | 54.4 mm | 7 |
| 17.7 mm | 55.7 mm | 7.5 |
| 18.1 mm | 57.0 mm | 8 |
| 18.9 mm | 59.5 mm | 9 |
| 19.8 mm | 62.1 mm | 10 |
Sizes 6 and 6.5 cover a large share of women's engagement rings in Canada, and 9 to 10 covers most men's bands. That is a starting point for a guess, not a substitute for measuring.
No ring to borrow? Paper, string, or a plastic sizer
A paper strip beats string. String stretches, and stretch always reads small.
- Cut a strip of paper about 5 mm wide and 100 mm long. Printer paper is fine; card stock is too stiff.
- Wrap it around the base of the finger and pull it snug, not tight. You should feel contact all the way round with no pinching.
- Slide the loop over the knuckle while it's still wrapped. If it won't pass, loosen it until it will, then mark it there.
- Mark where the end overlaps, unwrap, and measure to the mark in millimetres.
- Match that circumference to the chart above. If you land between two sizes, note both.
Do this three separate times, hours apart, and use the largest result. One measurement tells you what a finger was doing at one moment.
On buying a sizer
A plastic belt-style multi-sizer costs about $3 to $8 CAD and works well. A set of steel ring gauges is genuinely more accurate and costs $25 to $40 CAD, but it is more tool than most people need for one ring in their lifetime. Skip it unless you're sizing several people.
Printable paper sizers are free and fine, with one condition: print at 100% scale with page scaling turned off, then check the printed ruler against a real one before you trust it. Most bad printable results come from a printer helpfully shrinking the page by 4%.
When you measure matters as much as how
Fingers change size through the day. Half a size of swing is normal, and a full size is not unusual. The things that move the number:
- Temperature. Cold hands read small. Measuring outdoors in a Canadian February will give you a size you can't get past your knuckle in July.
- Time of day. Fingers are smallest first thing in the morning and largest in the late afternoon and evening.
- Salt and alcohol. The day after a big meal or a few drinks, fingers run large.
- Exercise. Right after the gym is the worst possible time to measure.
- Pregnancy, medication changes, and flying. All shift fingers noticeably and temporarily.
Measure at the end of a normal day, at room temperature, when hands are neither cold nor swollen. That's the size the ring has to live in most of the time.
Knuckles, band width, and when to size up
The ring has to pass the knuckle and then sit without spinning. When those two demands conflict, the knuckle wins, and you accept a slightly loose fit at the base. If the gap is large, a jeweller can add sizing beads or a small bar inside the shank to hold it in place. That's a $50 to $100 CAD job at most benches and it works well.
Band width matters more than people expect. A wide band, roughly 6 mm and up, sits tighter than a narrow one at the same nominal size. If you're choosing a wide band, go a quarter to a half size up from your measured size. For a standard 1.8 to 2.5 mm engagement ring shank, measure and order as-is.
Comfort-fit bands, which are domed on the inside, also run a touch large. Half a size down is the usual adjustment there.
Sizing a proposal ring without asking
You have a few options, in rough order of how well they work:
Borrow a ring she already wears on that finger and measure it, or press it into a bar of soap and measure the impression. Ask her mother or a close friend, who often already knows. Compare hand size against someone whose size you do know. Or buy a cheap costume ring in your best guess and watch whether it fits.
Guessing is a legitimate strategy for a surprise. If you're guessing, guess slightly large. A ring that goes on and spins a little is a small problem solved at a bench. A ring that won't go past the knuckle on the day is a bigger one.
Resizing later: what's easy, what isn't
Not every ring resizes the same way, and this is worth knowing before you choose a setting rather than after.
- Plain and pavé shanks in gold or platinum resize easily, usually one to two sizes in either direction. Typical bench charge in Canada is $60 to $150 CAD, more for platinum because it takes more heat and more finishing.
- Full eternity bands cannot be resized in any real sense. The stones go all the way around. You either remake the ring or you get the size right the first time.
- Rings with stones set close to the shank bottom, or with engraving that wraps the band, get complicated and expensive.
- Tungsten and ceramic cannot be resized at all.
If the setting you love is an eternity band, take the extra step and get measured on a steel mandrel at a jeweller before ordering. Home measurement is accurate to roughly half a size, which is fine for a solitaire and not fine for a ring that can never be adjusted.
What to do next
Measure at the end of the day, three times, and write down the number and the date. Then pick the setting first, since band width and setting style affect the size you should order. You can browse engagement ring settings and pair one with a natural or lab-grown stone from the loose diamond search, then see the two together in 3D before anything is made.
When you're ready, size, metal and engraving are all chosen at the finish your ring step, so you can hold the decision until you've measured properly. If you're still working out shape, budget or clarity, the other guides on the blog cover those.