What Ring Size Actually Is
A ring size is a number that corresponds to the inside circumference (or equivalently, the inside diameter) of the band. It is a measurement of the ring, not the finger — though the two are obviously related. The ring sizing systems used around the world are all attempting to describe the same physical reality, but they use different numbering conventions, which is why a US size 6 corresponds to a UK size L 1/2 corresponds to a Japanese size 12.
How US sizes work
The United States ring sizing system uses numerical sizes from 3 to 13 in standard increments, with half-sizes (5, 5.5, 6, 6.5, etc.) widely available and quarter-sizes (5.25, 5.75) available from many fine jewelers including Since Love. Each whole size up adds approximately 2.5 millimeters of inside circumference, or roughly 0.8 millimeters of inside diameter. The increment between adjacent sizes is small but perceptible — a half-size difference is easily felt on the finger.
The most common adult ring sizes in the US are size 6 to 7 for women and size 9 to 11 for men, but individual variation is substantial — finger size depends on bone structure, body composition, and which finger the ring is intended for. Knuckle size, finger length, and finger thickness all factor into the right size for a particular wearer. There is no single "average" size that fits most people.
Why international sizing is not standardized
Each major jewelry market developed its own sizing convention historically, and these conventions persist because the cost of switching is high. The UK and Australia use letter-based sizes from A to Z. Japan uses numerical sizes from 1 to 30. Hong Kong uses a numerical system that does not correspond to any other. Europe uses inside circumference in millimeters directly. None of these systems are wrong; they are simply different reference frames pointing to the same physical measurement.
A complete cross-reference chart between all major systems appears in Chapter II. For Since Love clients shopping internationally, the chart allows direct conversion. If you know your size in any one system, you know your size in all of them.
Even within a single country, ring sizing is not perfectly standardized between manufacturers. A US size 6 from one jeweler may be very slightly different from a US size 6 from another — typically by 0.1 to 0.2 millimeters of inside diameter, which is barely perceptible but can matter for a ring intended to fit precisely. This is why most fine jewelers offer free resizing within a reasonable window after delivery; we offer it complimentary within 60 days of delivery. The sizing chart is a guide, not a guarantee.
International Ring Size Chart
The chart below cross-references inside diameter and circumference (in millimeters and inches) against the major regional ring sizing systems used worldwide. Find your size in any one column to read it across all the others. All Since Love rings are crafted in standard US sizes; this chart allows international clients to convert their familiar local size to its US equivalent before ordering.
| Inside Dia. (mm) | Inside Circ. (mm) | Inches | US · Canada | UK · Australia | Europe | Japan | Hong Kong | Singapore | Switzerland |
|---|---|---|---|---|---|---|---|---|---|
| 14.1 | 44.2 | 1.74 | 3 | F | 44 | 4 | 6 | 4 | 4 |
| 14.4 | 44.8 | 1.77 | 3.25 | F 1/2 | 45 | — | — | — | 4 5/8 |
| 14.5 | 45.5 | 1.79 | 3.5 | G | 45.5 | 5 | 7 | — | 5 1/4 |
| 14.7 | 46.1 | 1.82 | 3.75 | G 1/2 | 46 | — | — | — | 5 7/8 |
| 14.9 | 46.8 | 1.84 | 4 | H | 47 | 7 | 8 | 5 | 6 1/2 |
| 15.1 | 47.4 | 1.87 | 4.25 | H 1/2 | 47.5 | — | — | — | 7 1/8 |
| 15.3 | 48.0 | 1.89 | 4.5 | I | 48 | 8 | 9 | — | 7 3/4 |
| 15.5 | 48.7 | 1.92 | 4.75 | J | 48.5 | — | — | — | 8 3/8 |
| 15.7 | 49.3 | 1.94 | 5 | J 1/2 | 49 | 9 | 10 | 9 | 9 |
| 15.9 | 50.0 | 1.97 | 5.25 | K | 50 | — | 11 | — | 9 5/8 |
| 16.1 | 50.6 | 1.99 | 5.5 | K 1/2 | 50.5 | 10 | — | 10 | 10 1/4 |
| 16.3 | 51.2 | 2.02 | 5.75 | L | 51 | — | 12 | 11 | 10 7/8 |
| 16.5 | 51.9 | 2.04 | 6 | L 1/2 | 52 | 11 | 13 | 12 | 11 1/2 |
| 16.7 | 52.5 | 2.07 | 6.25 | M | 52.5 | — | — | — | 12 1/8 |
| 16.9 | 53.1 | 2.09 | 6.5 | M 1/2 | 53 | 13 | 14 | 13 | 12 3/4 |
| 17.1 | 53.8 | 2.12 | 6.75 | N | 54 | — | — | — | 13 3/8 |
| 17.3 | 54.4 | 2.14 | 7 | N 1/2 | 54.5 | 14 | 15 | 14 | 14 |
| 17.5 | 55.1 | 2.17 | 7.25 | O | 55 | — | 16 | — | 14 5/8 |
| 17.7 | 55.7 | 2.19 | 7.5 | O 1/2 | 56 | 15 | — | 15 | 15 1/4 |
| 17.9 | 56.3 | 2.22 | 7.75 | P | 56.5 | — | 17 | — | 15 7/8 |
| 18.1 | 57.0 | 2.24 | 8 | P 1/2 | 57 | 16 | — | 16 | 16 1/2 |
| 18.3 | 57.6 | 2.27 | 8.25 | Q | 58 | — | 18 | — | 17 1/8 |
| 18.5 | 58.3 | 2.29 | 8.5 | Q 1/2 | 58.5 | 17 | — | 17 | 17 3/4 |
| 18.8 | 58.9 | 2.32 | 8.75 | R | 59 | — | — | — | 18 3/8 |
| 19.0 | 59.5 | 2.34 | 9 | R 1/2 | 60 | 18 | 20 | — | 19 |
| 19.2 | 60.2 | 2.37 | 9.25 | S | 60.5 | — | — | — | 19 5/8 |
| 19.4 | 60.8 | 2.39 | 9.5 | S 1/2 | 61 | 19 | 21 | 19 | 20 1/4 |
| 19.6 | 61.4 | 2.42 | 9.75 | T | 61.5 | — | — | — | 20 7/8 |
| 19.8 | 62.1 | 2.44 | 10 | T 1/2 | 62 | 20 | 22 | — | 21 1/2 |
| 20.0 | 62.7 | 2.47 | 10.25 | U | 63 | 21 | — | — | 22 1/8 |
| 20.2 | 63.4 | 2.49 | 10.5 | U 1/2 | 63.5 | 22 | 23 | 22 | 22 3/4 |
| 20.4 | 64.0 | 2.52 | 10.75 | V | 64 | — | — | — | 23 3/8 |
| 20.6 | 64.6 | 2.54 | 11 | V 1/2 | 65 | 23 | 24 | 23 | 24 |
| 20.8 | 65.3 | 2.57 | 11.25 | W | 65.5 | — | — | — | 24 5/8 |
| 21.0 | 65.9 | 2.59 | 11.5 | W 1/2 | 66 | 24 | 25 | — | 25 1/4 |
| 21.2 | 66.6 | 2.62 | 11.75 | X | 67 | — | — | — | 25 7/8 |
| 21.4 | 67.2 | 2.65 | 12 | X 1/2 | 67.5 | 25 | 27 | 25 | 26 1/2 |
| 21.6 | 67.8 | 2.68 | 12.25 | Y | 68 | — | — | — | 27 1/8 |
| 21.8 | 68.5 | 2.71 | 12.5 | Z | 69 | — | — | 26 | 27 3/4 |
| 22.0 | 69.1 | 2.72 | 12.75 | Z 1/2 | 69.5 | — | — | — | 28 3/8 |
| 22.2 | 69.7 | 2.75 | 13 | — | 70 | 27 | — | 27 | 29 |
If you know your ring size in any system, find it in the corresponding column and read across the row to see your size in all other systems. The inside diameter and circumference columns on the left are the underlying physical measurement — they are what every regional system is converting from in different ways. If you have measured your finger directly with a string and ruler, the inside circumference column is your most direct match.
How to Measure at Home
Four methods cover virtually every home-measurement scenario, ranging from the immediate and approximate to the most accurate possible without an in-person fitting. The right method depends on the time you have, the tools available, and how precise the measurement needs to be. If you are buying a daily-wear engagement ring or wedding band, we strongly recommend the free mailable ring sizer described in Method Four; it is the most accurate at-home option by a meaningful margin.
String & Ruler Method
Basic AccuracyThe simplest at-home method, requiring nothing more than a piece of string or paper, a ruler, and a pen. Useful for getting a working approximation of your size when no other tools are available, but the least accurate of the four methods — the natural give of string and the difficulty of marking precisely produce typical errors of half a size or more.
- Wrap a piece of non-stretchy string or a thin strip of paper around the base of the finger you intend to size.
- Mark the point where the string overlaps itself, using a fine-tip pen for precision.
- Lay the string flat against a ruler with millimeter markings and measure to the marked point.
- Match the resulting measurement to the Inside Circumference column of the chart in Chapter II to find your US size.
Existing Ring Method
Medium AccuracyIf the wearer already owns a well-fitting ring on the same finger, that ring is itself a reliable measurement instrument. This method is particularly useful for surprise engagements — you can borrow a ring without the wearer's awareness, measure it discreetly, and replace it before the absence is noticed.
- Select a ring the wearer currently wears comfortably on the intended finger — typically the ring finger of the left hand for engagement rings.
- Measure the inside diameter of the ring using a ruler with millimeter markings, edge to edge across the widest interior point.
- Alternatively, place the ring over progressively-sized printed circles (the printable PDF in Quick Actions includes this format) until the ring's inside edge matches a circle exactly.
- Match the diameter measurement to the Inside Diameter column of the chart in Chapter II to find the US size.
Printable PDF Sizer
High AccuracyA printable plastic-sizer-equivalent tool you can produce at home with a standard printer. The PDF includes a measuring strap that wraps around the finger and a circle reference grid for measuring existing rings — combining both methods above in a single calibrated tool. Critical: print at 100% scale, no fit-to-page, and verify the calibration mark is exactly the stated length before use.
- Download the PDF from the link below and print on standard letter or A4 paper at 100% scale with no auto-fit or shrink-to-fit settings enabled.
- Verify the printed calibration line matches its stated length using a ruler — if it does not, your printer is scaling and the result will be inaccurate.
- Cut along the dashed lines to separate the strap-style sizer and the circle reference grid.
- Wrap the paper sizer around the intended finger, snug but not tight, and read the size at the cross-reference arrow.
Free Mailable Ring Sizer
Highest AccuracyA reusable plastic ring sizer mailed to you anywhere in the world, complimentary. The sizer is unisex, reusable, and engineered to mimic the feel of an actual ring on the finger — producing the most accurate at-home measurement possible without an in-person fitting. We mail to clients in any country at no charge, including return-shipping for the sizer if desired (it is yours to keep otherwise).
- Request your free sizer using the form in Chapter VII (or the link in the Quick Actions panel above) — we ship to all countries worldwide at no charge to you.
- When the sizer arrives, wrap it around the intended finger and adjust until the fit feels comfortable — snug but not tight, with mild resistance over the knuckle.
- Read the size at the cross-reference arrow on the sizer; the result is calibrated to standard US ring sizes.
- For the most accurate result, measure in the evening after a typical day of activity, when fingers are at their normal everyday size.
All paper, string, and printable methods share a common limitation: they do not replicate the feel of an actual ring around the finger. An actual sized ring sits differently than paper or string, with different friction over the knuckle and different pressure at the base of the finger. The plastic mailable sizer is engineered specifically to replicate this feel — which is why it produces measurements within 0.1 size of the actual ring. For a piece you will wear daily for decades, the extra week of waiting for delivery is the right trade.
How a Ring Should Fit
A correctly-sized ring fits with just enough resistance to require effort over the knuckle, then settles comfortably at the base of the finger without spinning, sliding, or pinching. The most common sizing mistakes are erring too loose (because tight feels alarming when first put on) or erring too tight (because the wearer fears losing it). Both result in a ring that is unsatisfying to wear daily for the next forty years.
Knuckle pass · Base settle
A correctly-sized ring passes two specific tests. If both succeed, the size is right. If either fails, the ring is the wrong size in the direction the test indicates.
Knuckle Pass Test
The ring slides over the knuckle with mild but noticeable resistance — enough that you feel it, not so much that it requires force or causes discomfort. A small amount of friction at the knuckle is correct and protects against the ring slipping off in cold weather or after weight loss.
Base Settle Test
Once past the knuckle, the ring settles at the base of the finger and sits comfortably with minimal rotation when the hand is relaxed. You should be aware of the ring's presence but not actively distracted by it. Slight rotation when actively flexing the finger is normal.
If knuckle requires force
If the ring requires significant force or causes pain going over the knuckle, it is too small. A ring that requires soap or lubricant to put on or remove is unambiguously the wrong size and should be sized up half to a full size.
If knuckle resistance is absent
If the ring slides over the knuckle with no perceptible resistance whatsoever, or if the ring spins freely at the base of the finger when the hand is relaxed, the ring is too large. The risk is loss in cold weather, when fingers contract.
The width factor
A ring's band width affects how a given size feels on the finger. A wide band (6mm or more) feels tighter than a thin band (2mm) of the same nominal size, because more surface area is in contact with the skin. Many wearers who size confidently in a thin band need to size up by a quarter or half size for a wide band to maintain the same comfort feel.
If you are sizing for a wedding band that will be wider than the engagement ring it sits next to, expect this dynamic. If you are sizing for a comfort-fit band (a band with a rounded inner edge designed to slide over the knuckle more easily), the same width effect applies but is partially offset by the comfort fit. When in doubt, size up — a slightly loose ring is more comfortable for daily wear than a slightly tight one.
If a ring is comfortable when first put on but feels increasingly tight by the end of a hot day, the size is correct — fingers swell normally throughout the day. If a ring is comfortable in the morning and slips off easily by evening, it is slightly too loose. If a ring is uncomfortably tight first thing in the morning, it is too small for any time of day. The morning ring fits when you first wake up; the evening ring fits at end of day; the right ring fits comfortably at both times.
Timing & Special Situations
Finger size is not constant throughout the day or across the year. Temperature, hydration, sodium intake, exercise, time of day, and pregnancy all produce measurable shifts in finger circumference. For a ring meant to be worn daily, the goal is to find the size that fits at the wearer's typical baseline — not the largest size, not the smallest, but the size that fits comfortably most of the time. The situations below are the ones we encounter most often in practice.
Time of Day
Variation: 0.25 to 0.5 sizeFingers are at their smallest in the morning after sleep, then gradually swell over the course of the day with activity, hydration, and ambient warming. By evening, after a full day of typical activity, fingers reach their baseline working size. Measure in the evening, between roughly 5pm and 8pm, when fingers are at this stable end-of-day baseline. Morning measurements consistently size too small; mid-day measurements depend heavily on what you have been doing.
Temperature & Climate
Variation: 0.25 to 0.75 sizeFingers contract in cold weather and expand in heat. The variation between a winter morning and a summer afternoon can exceed three quarters of a size for the same person. If you live in a climate with significant seasonal swings, size for an average day rather than either extreme. If you travel frequently between climates, prioritize fit at your home climate. Cold-weather fit being slightly loose is acceptable; hot-weather fit being slightly tight is not, because hot-weather swelling can make a too-tight ring genuinely difficult to remove.
The Surprise Engagement
Most common scenarioIf you are buying an engagement ring for someone without their knowledge, you have three reliable options for sizing. Borrow a ring they currently wear on the same finger and use Method 02 above to measure it — the most common discreet approach. Ask a trusted friend or family member of the recipient to confirm their size or borrow a ring on your behalf. Or order at the most likely size and use our complimentary 60-day resizing to adjust after the proposal. The third option is honestly the most foolproof: a ring that needs resizing is a small inconvenience; a wrong-size ring on the day of the proposal is recoverable but anxious.
Pregnancy & Postpartum
Variation: 0.5 to 2.0 sizesPregnancy produces fluid retention that often expands ring size by half a size or more, with the largest changes typically in the third trimester. Postpartum, finger size returns toward the pre-pregnancy baseline over weeks to months, but for some women the change is partially permanent. If you are sizing during pregnancy, size for the pre-pregnancy state and use our resizing service if needed afterward. Many wearers temporarily wear engagement and wedding rings on a chain during pregnancy rather than resizing twice.
Weight Fluctuation
Variation: 0.5 to 2.0+ sizesSignificant weight changes affect ring size, with finger size typically changing by approximately half a ring size for every ten pounds of body weight change in adults. If you anticipate substantial weight change in either direction over the next year (intentional weight loss program, medical changes, or fitness regimen), discuss this with us at the time of order — for some clients we recommend sizing slightly large and resizing down later, rather than trying to predict the destination weight precisely. Our complimentary resizing is available within 60 days of delivery.
In our experience, the most common sizing regret is not measuring at the right time of day. A ring measured at 7am after a cool night and a low-sodium dinner the previous evening will size half a size smaller than the same finger measured at 7pm after a warm day. The result is a ring that feels comfortable when first delivered but increasingly tight as daily life produces ordinary finger swelling. Always measure in the evening at typical baseline.
Our Sizing & Resizing Service
Even with careful measurement, sizing is occasionally imperfect — finger size changes over the years, climates change, life changes. We offer complimentary resizing within 60 days of delivery on eligible designs. The four commitments below govern how we handle sizing for every Since Love client, before and after delivery. The verification happens whether anyone is watching.
Four commitments that govern every sizing question
These standards apply to every Since Love piece, regardless of price tier, design complexity, time elapsed since purchase, or whether the client asks. Sizing should not be a billable event for any reasonable adjustment.
A reusable plastic ring sizer, mailed to any country worldwide at no charge to the client. Engineered to mimic the feel of an actual ring, accurate to 0.1 size or better with proper use. The sizer is yours to keep; we do not require return shipping. Request the sizer using the form at the end of this page.
Every Since Love ring is eligible for complimentary resizing within reasonable bounds (typically ±3 sizes from original) within 60 days of delivery. Requests outside the 60-day window may incur a service fee. The client covers shipping in both directions for resizing requests; the resizing labor itself is complimentary.
If the ring as delivered does not fit on first wear — whether because measurement was off, finger size changed in the interim, or the wearer's finger reacts differently to the actual ring than to a sizer — we offer a thirty-day exchange or a resize within 60 days of delivery at no charge including return shipping. The exchange window is thirty days of delivery; the complimentary resizing window is 60 days of delivery, subject to design eligibility.
Some ring designs cannot be resized without rebuilding the piece — full eternity bands with stones around the entire circumference, certain channel-set designs, and rings of titanium or tungsten. We disclose this at the time of purchase rather than after, so the client can choose whether the design constraint is acceptable. For non-resizable Since Love designs, we offer remake-at-cost service if a major fit issue arises.
Print Our Ring Sizer
A printable PDF with a plastic-sizer-equivalent grid: a wrap-around strap sizer, a circle reference grid for measuring existing rings, and step-by-step instructions on a single page. Print at 100% scale with no fit-to-page setting, verify the calibration mark, then follow the steps.
The Since Love Printable Ring Sizer
Our printable PDF includes a wrap-around strap sizer, a complete circle reference grid for measuring existing rings, and step-by-step instructions on a single page. Print at 100% scale with no fit-to-page setting for accurate results. Both letter and A4 versions are included in the file.
Request Your Free Ring Sizer
For the most accurate at-home measurement possible, we mail a reusable plastic ring sizer to any country in the world, complimentary. The sizer is engineered to mimic the feel of an actual ring on the finger, producing measurements accurate to 0.1 size or better. There is no obligation associated with the request; the sizer is yours to keep, and we will not contact you about products beyond shipping confirmation unless you opt in below.
A free ring sizer, mailed to you anywhere in the world.
Tell us where to send it. We ship to every country we serve, including the United States, United Kingdom, all of the European Union, Canada, Australia, New Zealand, Singapore, Hong Kong, Japan, and beyond. Delivery takes approximately 5 to 14 days depending on destination.
- Reusable plastic, unisex, accurate to 0.1 size
- Calibrated to standard US ring sizes (3 to 13, half sizes included)
- Mimics the feel of an actual ring on the finger
- Yours to keep — no return required
- Complimentary worldwide shipping, no obligation
Sizing Questions
Answers to the questions clients ask most often about ring sizing, in the order we hear them. If your question is not covered, the easiest way to get a useful answer is to email info@sincelovejewelry.com.
Get the right size. Wear it for life.
Ring sizing can be simple with patience and the right method. Order our free mailable sizer if you have time, or use the printable PDF to start now. We’ll help you get it right the first time, and adjust it after delivery if needed. Our 60-day resizing commitment is real.