Learn how to read a ring mandrel for sizing and properly measure your customer’s fingers.

How To: Ring Size Reference Guide & Chart

Ring sizing is one of the most essential skills used by a jeweler, and it’s important to understand the intricacies of the service from every aspect of the job. From working with the customer to working with the ring, you’ll need to be meticulous with your measurements, so the final result is up to your standards. Let’s look at measurement processes that can help make your work more accurate.

How to Measure a Ring Size With Your Customer


Have the Right Tools

You should have a set of ring gauges that match your calibrated ring mandrel. This will ensure accuracy when moving from the customer to the bench. Our advice is to buy a set that includes both gauges and mandrels or buy them separately from the same brand. Make sure to have ring gauges with multiple widths and fits so you can properly measure according to the type of mounting.

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Know the Customer and Their Finger

Every customer’s finger is different, so you’ll need to understand the shape of their hand before beginning. Will their knuckles make it harder for a ring to move past? Do they have problems with swelling? The bottom line is that the ring will need to fit to their comfort.


Consider Environmental Factors

External influences have an impact on how rings fit on the finger. Temperature, time of day, humidity, geographic region, and season all play a part in finger size. Keep these factors in mind to make sure the final product remains comfortable for your customer.

Measuring Tools Intro Spread

How to Read a Ring Mandrel

Ring sizing itself is straight-forward. It involves either adding or removing a piece of metal from the shank of a ring to increase or decrease the diameter or ring size. When 2.61 millimeters are added or removed from the shank, it will change the ring by one full size (US sizing).

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The leading edge of the shank profile will be used to determine the actual size of the ring when placed on the mandrel. The leading edge is the first part of the shank that touches the mandrel. View the image below for an example of where the leading edge would be for common ring styles.

How To: Ring Size Reference Guide & Chart

When a ring is offered at a specific finger size or your customer requests a specific finger size, the ring should be true to size. However, it is acceptable for the ring to have a 1/8th finger size tolerance (up or down). If a ring’s size is 1/4th larger or smaller than the intended size, then the ring is out of tolerance, will not fit the customer properly, and should be resized.

How To: Ring Size Reference Guide & Chart

For example, these images show a flat-edge band at a size 9 being measured. The image to the left shows the ideal measurement. The second and third images from the left are deemed acceptable because they fall within a reasonable tolerance. The two images to the far right are deemed unacceptable because they fall outside a reasonable tolerance.

Need Help?

Hopefully, these tips provide some clarity on how to produce more consistent results in your ring sizing. If you have any questions, contact the Stuller Tools Tech Team at 800-877-7777, ext. 4300. This specialized team of industry experts is at your disposal to set you up for success.