A Toronto fine jewelry studio specializing in engagement rings and wedding bands defined by exacting craftsmanship and exceptional GIA and HRD graded diamonds. Each piece reflects precision, transparency, and a commitment to exceptional standards.
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Ring Size Chart & Guide
Quick Answer
To find your ring size in Canada: visit a jeweller who uses a calibrated finger gauge set — the most accurate method. At home, trace the inside of a ring you already wear on that finger and bring the tracing to a jeweller for measurement. The most common women’s ring size in Canada is US size 6–7 (inner diameter 16.5mm–17.3mm). The most common men’s ring size is US size 9–11 (inner diameter 19.0mm–21.0mm). In Canada and the United States, rings are sized on a numerical scale (sizes 3–13, in quarter-size increments) — different from the UK letter system or the Swiss numerical system. Use the international ring size chart below to convert between systems.
In this Guide
Why Accurate Sizing Matters
Ring size is not a preference — it is a precision requirement. The difference between a half size means roughly 0.4mm in inner diameter. At the scale of a finger, that is the difference between a ring that fits and one that does not.
For plain and simple solitaire shanks, resizing after production is straightforward. But many modern engagement ring designs are not forgiving of that approach. Pavé settings, channel-set bands, and rings with stone coverage that wraps the shank all have limited or zero resizing potential. Getting the measurement right before fabrication is not just advisable—for many designs, it is mandatory.
Planning a proposal? Our custom engagement ring process starts with a design consultation — sizing, proportion, and setting structure resolved before production begins. Read: The Lumi Design Process →
The Most Accurate Method: Jeweller Measurement
The most accurate way to find your ring size is a professional measurement by a jeweller using a calibrated finger gauge set. These are a series of metal bands in half-size increments that slide onto the finger to determine the correct fit. This method accounts for knuckle diameter, finger shape, temperature, and the specific width of the band being ordered—none of which home methods can fully address.
At Lumi Jewelry in Toronto, ring sizing is part of every engagement ring consultation. We take measurements across both hands and consider the exact profile and width of the design before confirming a size. For custom work, this step happens before the CAD phase begins — so the design is built to the right dimension from the start.
If visiting a jeweller in advance is not possible—when a proposal is intended to be a surprise, for example — there are secondary methods that can provide a working estimate.
At-Home Sizing Methods
1 — Trace an Existing Ring
Take a ring worn on the ring finger—with a plain, unadorned band for the most accurate result. Place it flat on a piece of white paper and trace the inner circle with a sharp pencil. Bring the paper to a jeweller, who can measure the inner diameter and match it to a ring size. This is more reliable than string or paper strip methods.
2 — Bar of Soap Impression
Press a ring worn on the ring finger firmly into a bar of soap until it leaves a clear impression on the surface. The resulting circle gives a jeweller a measurable diameter to work from. Wipe the ring clean of any residue before returning it. Per GIA’s guidance, this is among the more workable home methods available when a direct measurement is not possible.
3 — Printable Ring Sizer
Several online tools and some retailers offer printable ring sizer guides — paper rings that can be cut out, assembled, and slid onto the finger. These provide a reasonable starting estimate but are sensitive to printer scale settings and paper thickness. Always verify the printed scale against the reference measurement printed on the page before using.
4 — Ask Trusted Friends or Family
If none of the above is practical, a close friend or family member may already know the size—particularly a mother, sister, or close friend who has gone jewelry shopping together. This is especially useful for confirming a size estimate already derived from another method.
What to avoid: String-and-ruler and paper-strip methods are widely circulated online but consistently unreliable. String stretches; paper can shrink with humidity. Neither method accounts for knuckle diameter — which, for most people, is larger than the finger itself and must be cleared for the ring to sit correctly.
Factors That Affect Ring Fit
Temperature & Time of Day
Fingers contract in cold and expand in heat. A measurement taken on a cold winter morning may differ by a half size or more from one taken on a warm afternoon. The same applies to season: a ring sized in January may feel loose in July. Mid-afternoon, in a temperature-controlled room, is generally the most neutral measurement condition. GIA recommends factoring in weather, altitude, and time of day when determining size.
Dominant vs. Non-Dominant Hand
The dominant hand is typically about half a size larger than the non-dominant hand. For right-handed individuals, the left ring finger will usually be slightly smaller. Always specify which hand the ring is intended for when being measured. This distinction matters most when sizing from an existing ring worn on a different hand than the one the new ring will sit on.
Knuckle Size
For most people, the knuckle is larger than the base of the finger where the ring rests. A ring sized only at the base may not pass over the knuckle at all. The correct size must be large enough to clear the knuckle while still fitting securely at the finger base. For fingers where the knuckle-to-base difference is significant, a hinged or expandable shank may be worth considering.
Altitude & Swelling
Air travel and high altitude can cause fingers to swell temporarily due to changes in cabin pressure. Pregnancy, medication, and certain health conditions can also cause persistent size changes. If there is any known history of significant size fluctuation, design choices should account for this from the start — selecting a setting that allows resizing is a structural decision, not just a preference.
Canadian Sizing Standards
In Canada, ring sizing follows the US numerical scale — sizes 3 through 13, measured in quarter-size increments. This is different from the UK letter system (F through Z1) used in the United Kingdom and Australia, and from the Swiss numerical scale used in continental Europe. When ordering from an international retailer or comparing a size across borders, always convert using the millimetre inner diameter as the reference point. It is the only universally consistent measurement — a US size 6 is 16.5mm regardless of which country produced the ring.
Design consideration: When a ring cannot be resized after production — full eternity bands, fully pavéd shanks — the sizing process becomes part of the structural brief. At Lumi Jewelry, we discuss resizing potential during the design consultation before the CAD file is finalized.
Band Width and Sizing Adjustments
Band width affects fit. A wider band exerts more surface pressure against the finger, which makes the same nominal size feel tighter than a narrow band of identical diameter. As a general starting point:
Width-to-Size Guidelines
Under 4mm: Standard sizing typically applies without adjustment.
4mm–6mm: A half-size increase may be appropriate depending on finger shape and setting style.
6mm and above: A half- to full-size increase is generally recommended. Confirm with a jeweller using a gauge that matches the intended band width.
Stacked rings: When a wedding band will be worn alongside an engagement ring, both pieces occupy the same finger space. The cumulative width affects how each ring sits and moves. This is best evaluated as a system—with both pieces considered together during the sizing and design phase.
International Ring Size Chart
Ring sizes are measured differently across markets. This ring chart below cross-references US/Canada sizing — the standard used at Lumi Jewelry in Toronto — with UK/Europe/Australia letter sizing, Swiss numerical sizing, and Asian sizing (Hong Kong, China, Singapore, Taiwan, Japan). Inner diameter and circumference are given in millimetres for direct reference.
The most common sizes for women (US/Canada 5–8) are highlighted. These represent approximately 70–80% of all engagement ring sizing — but individual anatomy varies considerably, and accurate measurement is always preferable to estimating from an average.
What Ring Size Is My Measurement in mm?
If you have already measured the inner diameter of an existing ring — or measured around your finger with a flexible tape — use this quick reference to find your US/Canada ring size. These are the most commonly searched millimeter-to-size conversions:
14.9mm = US size 4
15.3mm = US size 4.5
15.7mm = US size 5
16.1mm = US size 5.5
16.5mm = US size 6
16.9mm = US size 6.5
17.3mm = US size 7
17.7mm = US size 7.5
18.1mm = US size 8
18.5mm = US size 8.5
19.0mm = US size 9
19.4mm = US size 9.5
19.8mm = US size 10
20.2mm = US size 10.5
20.6mm = US size 11
21.0mm = US size 11.5
For sizes not listed, refer to the full chart above. All values are inner diameter in millimeters. Confirm with a jeweller before ordering—especially for settings that cannot be resized.
Which Rings Can Be Resized
Resizability is a design characteristic, not a guarantee. It depends on setting type, stone placement, and metal structure. Understanding this before committing to a design affects both the setting choice and how seriously the initial sizing needs to be taken.
Generally Resizable
Plain metal shanks — whether flat, domed, or knife-edged — can typically be resized up or down by 1–2 sizes without affecting structural integrity. Solitaire settings, bezel-set designs, and rings with stones only in the head (not along the shank) fall into this category. Resizing is a standard service for these styles.
Limited Resizing
Pavé and channel-set shanks can sometimes be adjusted, but the range is narrow — typically no more than half a size in either direction without risk of disturbing the stone setting. Wide bands and designs with decorative shank detail also have limited adjustment potential. Getting the size right before production is the design-responsible approach for these styles.
Cannot Be Resized
Full eternity bands — with stones running the complete circumference of the shank — cannot be resized after production. There is no plain metal section to work with. The same applies to rings with continuous stone coverage or highly structural shanks where the metal integrity cannot be compromised. For these designs, sizing is finalised before the CAD file is approved.
If you are unsure about sizing before production: Choose a setting style that allows for adjustment. A solitaire or simple bezel design built to an estimated size can be corrected. A fully pavéd eternity band built to the wrong size cannot. This is a design decision, not just a practical one.
Get Your Ring Size Right — Before Production
At Lumi Jewelry, sizing is part of the design process. We take accurate measurements in our Toronto studio and build every custom engagement ring to confirmed dimensions before the CAD phase begins. No guesswork at the production stage.
Arrange a complimentary private consultation at our Toronto studio.
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