Considerations for Taking Accurate Measurements of a Finger or Ring


Female hand featuring a properly fitted platinum solitaire

When placed on a finger, the ring must pass the finger joint

Ring remains upright and does not turn freely

Ring does not come off easily

Sizing a ring requires an accurate measurement of the customer’s finger or ring

Tools to Determine Finger or Ring-Size Measurements

Tools that are used for accurately measuring finger or ring size

Narrow finger sizing gauges

Finger-sizing gauges are used to determine finger size. They are marked in whole and half sizes. The narrow-finger sizing gauge measures fingers for narrow rings such as solitaire rings or narrow bands (up to 4 mm in width).

Finger-sizing gauges are also available with convex inner surfaces

Wide finger sizing gauges

Wide-finger sizing gauges are used to determine finger size for wide rings such as fashion rings and wide bands (over 4 mm in width)

Plastic graduated ring mandrel, showing sizes in ¼ size increments

The size of a customer’s ring is determined using a ring sizing stick or ring mandrel made of tapered wood, plastic, or aluminum that is marked in quarter, half, and full-size increments (These increments equate to inside diameter increases of approximately 0.2 mm, 0.4 mm and 0.8 mm respectively).

To do sizing work, bench jewelers use a steel ring mandrel made of tapered, milled steel; and marked in quarter, half, and whole sizes (0.2 mm, 0.4 mm and 0.8 mm, inside diameter respectively).

All finger-sizing gauges, ring sticks, and ring mandrels must be calibrated to one another so measured sizes are consistent throughout a retail store, a trade shop, or a manufacturing company

Calibration of tools is important for operations with multiple locations, such as a retail store that sends work to a trade shop, or manufacturing companies that do special orders or custom work for retailers

Potential Problems and Engineering Features

Avoiding problems by using the right tools and techniques to measure ring and finger size.

Two platinum ring examples showing exposed culets

Always check if a mounted gemstone’s culet protrudes into the finger hole. If it does, a ring-sizing stick or mandrel with a groove must be used to prevent damage to the stone.

Sizing or handling a ring with an exposed culet is not advisable. This is considered a design flaw and a jeweler cannot safely and accurately size the ring without risk of damage. In this situation, consider an alteration, a change of setting, or a remount.

Measuring Finger Size

Techniques to Measure Finger Size

Jewelers’ steel tapered mandrel with a groove

To size a ring for a customer, measure the finger using a ring-sizing gauge with a width that most closely matches the finger

The correct size should be just loose enough to pass over the finger joint and settle at the position on the finger where the ring will be worn

Gently slide the finger-sizing gauge onto the customer’s finger. Never force it over the joint.

Every hand is unique. Judge each fitting on a case-by-case basis to determine what ring size is most comfortable for the customer.

Close-up of customer using narrow finger sizing gauges to confirm accurate size

Allow the customer to put the finger-sizing gauge on and take it off

Because fingers swell and contract, a finger size should be taken on three different occasions to confirm the measurement

Alternate between sizes in the event that the customer wants the finished ring to fit snugly or loosely

Close-up of jeweler writing customer sizing information on job envelope

Record the size on the job envelope, along with any special instructions, such as requests to preserve special engraving

Be sure to indicate the finger for which the ring is being sized

Best Practices for Determining Accurate Ring Sizes

Techniques and Tools to Measure Ring Sizes

Close-up of jeweler checking size of platinum solitaire on tapered ring mandrel

Sometimes, a customer wants to check the size of a ring that fits comfortably. To take these measurements, use a ring stick or mandrel.

For accuracy, be sure the new ring is the same shape or configuration as the sample ring. Determine if the ring being measured is round. If the shape is distorted, gently round it with a rawhide or nylon hammer on a steel-ring mandrel before determining size.

Slide the ring gently onto the ring stick until it is snug, but do not force it as the measurement could be inaccurate

Close-up view of platinum solitaire positioned on plastic ring mandrel to check ring size. In this illustration the ring is transparent so that the size is visible.

This customer’s ring is a size 6.75 (17.1 mm inside diameter).

Standard Rings of Even Width

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To measure a finger for a solitaire or band of even width (1 to 4 mm), use the narrow finger-sizing gauges

On the ring stick, read the ring size at the line on the stick where it touches the central point of the width. This example is a size 9.0 (19.0 mm inside diameter).

Tapered Rings

Close-up view of tapered band positioned on plastic ring mandrel to check ring size. In this illustration the tapered band is transparent so that the size is visible.

Use narrow gauges to measure tapered rings from 5 to 7 mm at the widest area to a narrower width of 2 to 3 mm

Determine the size at the line where the central point of the narrowest part of the ring touches the ring stick. The narrowest part of the ring might be the top or the bottom of the shank. This ring is size 5.25 (15.9 mm inside diameter).

Close-up view of tapered band positioned on plastic ring mandrel to check ring size.

Determine the size at the line where the central point of the narrowest part of the ring touches the ring stick. The narrowest part of the ring might be the top or the bottom of the shank. This ring is size 6.50 (16.9 mm inside diameter).

Wide Rings and Bands

To measure a ring wider than 4 mm, use the wide-finger sizing gauges. Do not force the finger-sizing gauge over the joint.

Wide rings have more metal that contacts the skin, and fit more tightly on the hand

On a ring stick, the size is determined at the line on the mandrel that touches the central point of the ring’s width. In this example, the band is a size 7 (17.3 mm inside diameter).

Close-up view of wide, tapered band positioned on plastic ring mandrel to check ring size

Wide rings might need to be one-half to one full size (approximately 0.4 mm to 0.8 mm US finger size inside diameter) larger than narrow rings, depending on the finger joint size and the customer’s comfort.

Even if a customer feels they know their ring size, always check it. This tapered ring is a size 6.75 (17.1 mm inside diameter).

Bridal Sets

Close-up view of engagement ring and wedding band set with diamonds, prior to being soldered together

Bridal sets wider than 4 or 5 mm when the band and engagement ring are worn together require special consideration

To prevent loss or damage before the rings are joined together, the engagement ring might have to be adjusted while being worn alone

Close-up view of wedding set positioned on plastic ring mandrel to check ring size.

Measure the bride-to-be’s finger using a wide-finger sizing gauge. However, rings worn individually might be loose, especially when her hands are cold.

When the rings are soldered together, they can be resized as a unit. However, this means there is potential for an additional sizing joint on the engagement ring.

Convex Interior – Rings or Bands

Close-up view of band with convex inside shank positioned on plastic ring mandrel to check ring size. In this illustration the band is transparent so that the size is visible.

Convex interiors of rings or bands are beveled inward from the edges of the shank

To fit a ring with a convex inside shank, use the narrow-finger sizing gauge

Determine the size at the point where the center of the ring or band touches the sizing stick. Then measure one-quarter size smaller.

Close-up view of flat-top band positioned on plastic ring mandrel to check ring size. In this illustration the band is transparent so that the size is visible.

Size the ring one-quarter size smaller than the measured finger size. For example, if the size 7 (17.3 mm inside diameter) gauge fits, size the ring to a 6.75 (17.1 mm inside diameter).

In these examples, the flat-top band is a size 5.5 (16.1 mm inside diameter) and the half-round band is a 6.75 (17.1 mm inside diameter).

Rings with Open Space Above the Finger

Close-up view of ring with open space between the top of the finger and the mounting

These rings have less metal in contact with the finger. Because they fit the hand more loosely, they will need to be sized smaller. The size adjustment depends on the distance between the ends of the shank and the opening.

To fit a ring with space between the top of the finger and the mounting, use the appropriate finger-sizing gauge (narrow for shanks less than 4 mm wide and wide for those greater than 4 mm wide). If the opening is 3 mm to 5 mm, subtract at least a quarter-size from the measured ring size.

Close-up view of ring with open space between the top of the finger and the mounting, positioned on plastic ring mandrel to check ring size. In this illustration the band is transparent so that the size is visible.

Determine the size at the point where the center of the narrowest part of the ring touches the ring stick. Then adjust the size according to the width of the opening at the top of the shank. With the opening at the top, this ring will fit a size 5.75 (16.3 mm inside diameter), not a 5.5 (16.1 mm inside diameter).

Special Circumstances

Perspective and side views of platinum solitaire with princess cut stones, featuring sizing beads at the 5:00 and 7:00 locations.

Every hand is unique. When measuring fingers and fitting rings, there may be special situations. Judge these on a case-by-case basis to determine what is most comfortable for the customer. Options exist for rings that cannot be sized or that are worn temporarily.

Although sizing beads can be a potential solution for keeping a ring from turning on the finger, they do not always satisfy customers. They take up about a half- size of space and tend to be uncomfortable to wear.

Soldering two small beads onto the inside of a ring shank is the simplest way to keep a ring from turning when the finger is 1.5 (1.2 mm US finger size inside diameter) or more sizes larger than the area where the ring sits.

Platinum five stone ring, featuring a horseshoe-shaped spring insert.

Installing a spring insert is an excellent way to keep a ring sitting straight on a finger. The spring, made of highly tensioned platinum, resembles a horseshoe and will hold the ring snugly. It is flexible and comfortable to wear, making it superior to sizing beads.

To maintain the tension or springiness of the insert, use a laser welder to install it. Using a torch will anneal the spring.

International Ring Size Chart

Another way to measure a ring is to take a measurement of the inside and determine the finger size from a standard chart. The inside of the ring must be perfectly round for this to work.

Featured Quality Assurance Benchmarks

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