Ring Size Calculator & Chart
Convert UK, Irish, US, European and international ring sizes and compare inner diameter and circumference measurements. Includes practical guidance for measuring and sizing vintage and antique rings.
Jewellery Tools & Calculators
Practical jewellery tools to help you compare ring sizes and estimate diamond and coloured gemstone carat weights. Use the calculators and reference guides when buying, identifying or comparing antique, vintage and preloved jewellery.
Diamond Carat Weight Calculator
Estimate diamond carat weight from millimetre measurements and compare common diamond sizes. The guide includes modern diamond shapes alongside old cuts and rose cuts often found in antique jewellery.
Coloured Gemstone Carat Weight Calculator
Estimate the approximate carat weight of coloured gemstones using their dimensions, shape and gemstone type, with guidance for sapphires, rubies, emeralds, garnets and other commonly used gemstones.
Using the Jewellery Calculators
These tools are designed to make jewellery measurements easier to understand. Ring sizes can be compared across different international sizing systems, while the diamond and gemstone calculators provide useful estimated carat weights when only millimetre measurements are available.
Carat weight calculations are estimates rather than exact measurements. Gemstone density, cutting proportions and depth can all affect the final weight. This is particularly relevant to antique diamonds and individually cut coloured gemstones. Exact carat weight requires a loose stone to be weighed on a calibrated gem scale.
Explore the Jewellery Guides
Looking for more information about antique and vintage jewellery? Explore practical guides covering hallmarks, precious metals, gemstones, diamonds, jewellery eras, identification, buying, collecting, care and sizing.
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