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Ring size converter

Convert a Tiffany / US ring size to the inside diameter and circumference listed in Tiffany's size chart.

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Ring size converter processes your input in this browser. Inputs and results are excluded from analytics. Recent tools save tool names, visit counts and last-visit times. Saved tools store only their names. Draft saving is optional and stays on this device; delete saved text with the draft controls. Loading text from a URL is optional and contacts that server; its URL and your IP address are visible to the server. An optional “Use in” action keeps a handoff in this tab. The next tool removes it on arrival and ignores it if more than a minute has passed.

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Answer

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Convert a Tiffany / US ring size to the inside diameter and circumference listed in Tiffany's size chart.

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Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
Saved scenario
Save the current answer, then change an input to compare. This clears when you leave.
Formula and assumptions
This uses Tiffany's chart, not a universal fit guarantee or a conversion for other national systems. Size labels require an exact listed half size. Measurements between rows show both neighboring sizes; try the ring to choose a fit. Diameters and circumferences are the rounded published measurements, so they need not exactly equal one another times pi. Ring width, finger shape and measurement error can affect fit.
Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
Reset reloads the tool with its starting values and releases open files and device controls. Saved drafts stay on this device until you delete them.
Links include your inputs and settings. Anyone with the link can see them, so leave out private text. Files and generated results are left out; random draws run again.
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Updated 
Using Ring size converter
Convert a Tiffany / US ring size to the inside diameter and circumference listed in Tiffany's size chart.
This uses Tiffany's chart, not a universal fit guarantee or a conversion for other national systems. Size labels require an exact listed half size. Measurements between rows show both neighboring sizes; try the ring to choose a fit. Diameters and circumferences are the rounded published measurements, so they need not exactly equal one another times pi. Ring width, finger shape and measurement error can affect fit.
Next: Length converter
Next: Unit converter
A worked example
Tiffany / US size 7 is listed with an inside diameter of 17.3 mm and circumference of 54.4 mm. A 54 mm circumference falls between the listed sizes 6.5 and 7.
Before you use the result
This uses Tiffany's chart, not a universal fit guarantee or a conversion for other national systems. Size labels require an exact listed half size. Measurements between rows show both neighboring sizes; try the ring to choose a fit. Diameters and circumferences are the rounded published measurements, so they need not exactly equal one another times pi. Ring width, finger shape and measurement error can affect fit.
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ToolOctopus. “Ring size converter.” Updated 2026-10-03. https://tooloctopus.com/ring-size-converter.
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