--- title: "What Size Pearls Should You Choose?" description: "A pearl size guide: how pearls are measured in millimeters, the usual sizes of Akoya, freshwater, Tahitian and South Sea pearls, and how size affects value." canonical_url: "https://learnaboutpearls.com/buying/pearl-size-guide/" last_updated: "2026-11-04" last_reviewed: "2026-10-26" reviewed_by: "Simon" publisher: "Unique Pearl" publisher_disclosure: "Learn About Pearls is published by Unique Pearl, a pearl jeweler." --- # What Size Pearls Should You Choose? **Short answer:** Pearls are measured across their diameter in millimeters, and each type grows within its own range: Akoya are typically 6 to 8 mm, freshwater pearls 3 to 15 mm, Tahitian pearls 8 to 14 mm and South Sea pearls 9 to 16 mm. When the other quality factors are equal, a larger pearl is rarer and worth more. So choose the type first, then a size within its range that suits your budget and the look you want. **Key facts:** - Pearl sizes are diameters in millimeters, and CIBJO's standards say any rounding must be down, never up. [1] - A drilled round pearl is measured across its widest diameter at right angles to the drill hole. [1] - When other value factors are equal, larger pearls are rarer and more valuable than smaller pearls of the same type. [2] - South Sea cultured pearls are the largest cultured pearls. [3] - The oyster that grows South Sea pearls is larger than the one that grows Japanese saltwater pearls, which gives it the potential for larger pearls. [2] - In the Japanese Akoya classification in CIBJO's guide, pearls of 8 mm or more count as large. [4] - A strand is described by the largest diameter of its largest pearl and the smallest diameter of its smallest. [1] Size is one of the seven [value factors](https://learnaboutpearls.com/glossary/#value-factors) used to judge [natural pearls](https://learnaboutpearls.com/glossary/#natural-pearl) and [cultured pearls](https://learnaboutpearls.com/glossary/#cultured-pearl), [2] but what counts as a large pearl depends on the type. ## How pearls are measured Pearl sizes are diameters in millimeters. CIBJO’s standards say measurements must be given accurately in millimeters, and any rounding must be downward, never up. [1] A single round pearl is measured across its widest diameter, or, if it is [drilled](https://learnaboutpearls.com/glossary/#drilled), across its widest diameter at right angles to the drill hole. Pearls of other shapes are described by their maximum length and their smallest and largest diameters. [1] For a strand, the description gives the largest diameter of the largest pearl and the smallest diameter of the smallest, whether the pearls are all about the same size or graduated. [1] On a report from SSEF, the Swiss gemological laboratory, a [graduated necklace](https://learnaboutpearls.com/glossary/#graduated-strand) gets diameters for the two smallest pearls, which are often the ones next to the clasp, two in between and the largest, and a necklace of pearls of about the same size also gets five diameters. [5] Natural pearls are also weighed. SSEF gives the weight of natural pearls in [carats](https://learnaboutpearls.com/glossary/#carat) and in [grains](https://learnaboutpearls.com/glossary/#pearl-grain), where 1 grain is 0.25 carat, and the weight of cultured pearls in carats only. [5] In the trade, CIBJO notes, cultured pearls may also be weighed in [momme](https://learnaboutpearls.com/glossary/#momme), [kan](https://learnaboutpearls.com/glossary/#kan), [liang](https://learnaboutpearls.com/glossary/#liang), carats or grams. [1] Pearl sizes from 2 to 16 mm, drawn to the same scale (not life-size). Drawn for Learn About Pearls. **Text version of this diagram** Eight circles in two rows, all drawn to one scale and each labeled with its diameter. The top row shows the four smallest sizes and the bottom row the four largest. Each circle is two millimeters wider than the one before it, so the largest is eight times as wide as the smallest. ## Typical sizes by type Each type grows within its own range. The table gives the typical sizes and the full range for each main type in the Learn About Pearls dataset. GIA cautions that pearls of every type can occur outside their typical ranges. [6] | Feature | Akoya cultured pearl | Freshwater cultured pearl | Tahitian cultured pearl | South Sea cultured pearl | | ------------ | ------------------------ | ------------------------- | ----------------------- | ------------------------ | | Typical size | 6–8 mm [4, 6, 7, 8, 9] | 3–15 mm [4, 6] | 8–14 mm [4, 6, 9, 10] | 9–16 mm [4, 6, 9] | | Size range | 2–11 mm [4, 6, 7, 8, 9] | 3–25 mm [4, 6] | 8–20 mm [4, 6, 9, 10] | 8–18 mm [4, 6, 9] | - **[Akoya](https://learnaboutpearls.com/glossary/#akoya)** are typically 6–8 mm, and Akoya over 10 mm are rare. [7, 8] In the Japanese Akoya classification in CIBJO’s guide, pearls of 3 to 4 mm are called [rin-dama](https://learnaboutpearls.com/glossary/#rin-dama), or extra small, 5 mm pearls are small, 6 to 7 mm pearls are medium, and pearls of 8 mm or more are large. [4] - **[Freshwater pearls](https://learnaboutpearls.com/glossary/#freshwater-cultured-pearl)** cover the widest range, typically 3–15 mm. [4] Most are small, and the larger ones are often bead-cultured. [6] - **[Tahitian pearls](https://learnaboutpearls.com/glossary/#tahitian-cultured-pearl)** are typically 8–14 mm, though CIBJO’s guide gives a wider typical range that starts at 4 mm. [4, 6] - **[South Sea pearls](https://learnaboutpearls.com/glossary/#south-sea-cultured-pearl)** are the largest cultured pearls, [3] typically 9–16 mm, with rare pearls over 20 mm. [4] - **[Keshi](https://learnaboutpearls.com/glossary/#keshi)**, which form without a bead, run from under 1 mm to 16 mm (larger ones are very rare). [1, 4] The difference starts with the animal. GIA notes that the oyster that grows South Sea pearls is larger than the one that grows Japanese [saltwater pearls](https://learnaboutpearls.com/glossary/#saltwater-pearl), which gives it the potential for larger pearls. [2] ## How size affects value When the other value factors are equal, larger pearls are rarer and more valuable than smaller pearls of the same type. [2] GIA counts size among the reasons South Sea pearls are valued, along with their thick [nacre](https://learnaboutpearls.com/glossary/#nacre), their long growth and the limited conditions they need. [11] Size is only one of the factors, though. GIA calls [luster](https://learnaboutpearls.com/glossary/#luster) perhaps the most important, and says numerous or severe surface blemishes can severely depress a pearl’s value. [2] The page [pearl quality](https://learnaboutpearls.com/quality/) explains each factor. ## Choosing a size Decide on the type first, because a size that is large for one type can be small for another. An 8 mm pearl counts as large in the Japanese Akoya classification, but it sits at the small end of the South Sea range. [4, 6] To see how big a size looks, the [pearl size visualizer](https://learnaboutpearls.com/tools/pearl-size-visualizer/) draws a pearl of the size you choose and can be set to life size on your screen. For a necklace, decide too whether the pearls should be all about the same size or graduated. In a graduated strand the pearls change in size along the strand, and the smallest are often the ones next to the clasp. [5] The page [necklace lengths](https://learnaboutpearls.com/buying/necklace-lengths/) covers how long a strand should be, and [what pearls are worth](https://learnaboutpearls.com/buying/what-are-pearls-worth/) covers price. To see how sizes look in finished jewelry, you can browse [Akoya cultured pearl stud earrings](https://www.uniquepearl.com/collections/pearl-earrings?pearl=akoya\&style=Stud\&utm_source=learnaboutpearls\&utm_medium=referral\&utm_campaign=buying\&utm_content=pearl-size-guide) from Unique Pearl, which publishes Learn About Pearls. ## Questions people ask ### How are pearls measured? Across the diameter, in millimeters. For a drilled round pearl, CIBJO's standards use the widest diameter at right angles to the drill hole; other shapes are described by their maximum length and their smallest and largest diameters. Any rounding has to be downward. [1] ### Why do bigger pearls cost more? Because they are rarer. GIA says that when the other value factors are equal, larger pearls are rarer and more valuable than smaller pearls of the same type. [2] ### Is an 8 mm pearl big? It depends on the type. In the Japanese Akoya classification in CIBJO's guide, 8 mm and up counts as large, while 8 mm is at the small end of the South Sea range. The oyster that grows South Sea pearls is larger, which gives it the potential for larger pearls. [2, 4, 6] ### Are pearls sold by weight? Natural pearls are weighed as well as measured. SSEF gives the weight of natural pearls in carats and in grains, where 1 grain is 0.25 carat, and that of cultured pearls in carats only. In the trade, CIBJO notes, cultured pearls may also be weighed in momme, kan, liang, carats or grams. [1, 5] ## References 1. CIBJO, The World Jewellery Confederation, Pearl Commission (2026). The CIBJO Pearl Book (Pearl Blue Book) 2026. [Source](https://cibjo.org/wp-content/uploads/2026/10/Pearl-Blue-Book-2026-.pdf) · [Archived copy](https://web.archive.org/web/20261025235254/https://cibjo.org/wp-content/uploads/2026/10/Pearl-Blue-Book-2026-.pdf) 2. Gemological Institute of America (GIA), Gem Encyclopedia. Pearl Quality Factors. [Source](https://www.gia.edu/pearl-quality-factor) · [Archived copy](https://web.archive.org/web/20261016075647/https://www.gia.edu/pearl-quality-factor) 3. Gemological Institute of America (GIA), Gem Encyclopedia. Pearl Buyer's Guide. [Source](https://www.gia.edu/pearl/buyers-guide) · [Archived copy](https://web.archive.org/web/20260613185853/https://www.gia.edu/pearl/buyers-guide) 4. CIBJO Pearl Commission (2025). CIBJO Guides Describing and Classifying Natural and Cultured Pearls, the Producing Molluscs & Responsible Pearling. [Source](https://cibjo.org/wp-content/uploads/2025/12/Final-Guide-October-2025-v2-COMPRESSED.pdf) · [Archived copy](https://web.archive.org/web/20260212155210/https://cibjo.org/wp-content/uploads/2025/12/Final-Guide-October-2025-v2-COMPRESSED.pdf) 5. Swiss Gemmological Institute SSEF. Pearls (SSEF reports). [Source](https://www.ssef.ch/reports/pearls/) · [Archived copy](https://web.archive.org/web/20260611191437/https://www.ssef.ch/reports/pearls/) 6. Gemological Institute of America (GIA), FAQ. What are the main types of cultured pearls and what are their distinctive characteristics?. [Source](https://www.gia.edu/FAQ/gia-faq-about-gemstones-cultured-pearl-types-characteristics) · [Archived copy](https://web.archive.org/web/20260510233833/https://www.gia.edu/FAQ/gia-faq-about-gemstones-cultured-pearl-types-characteristics) 7. Areeya Manustrong (2018). Very Small Akoya Cultured Pearls. [Source](https://www.gia.edu/gems-gemology/spring-2018-gemnews-very-small-akoya-cultured-pearls) · [Archived copy](https://web.archive.org/web/20260508145843/https://www.gia.edu/gems-gemology/spring-2018-gemnews-very-small-akoya-cultured-pearls) 8. Artitaya Homkrajae (2024). Remarkably Large Akoya Bead Cultured Pearls. [Source](https://www.gia.edu/gems-gemology/summer-2024-gemnews-large-akoya-bead-cultured-pearls) · [Archived copy](https://web.archive.org/web/20261025235607/https://www.gia.edu/gems-gemology/summer-2024-gemnews-large-akoya-bead-cultured-pearls) 9. Fisheries Agency of Japan (水産庁) (2026). 真珠養殖をめぐる情勢について (On the situation of pearl culture). [Source](https://www.jfa.maff.go.jp/j/saibai/attach/pdf/shinju-60.pdf) · [Archived copy](https://web.archive.org/web/20261026000052/https://www.jfa.maff.go.jp/j/saibai/attach/pdf/shinju-60.pdf) 10. Oïhana Latchere and others (2018). Influence of water temperature and food on the last stages of cultured pearl mineralization from the black-lip pearl oyster Pinctada margaritifera. [Source](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193863) · DOI [10.1371/journal.pone.0193863](https://doi.org/10.1371/journal.pone.0193863) · [Archived copy](https://web.archive.org/web/20260905233729/https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0193863) 11. Gemological Institute of America (GIA), Gem Encyclopedia. Pearl Description. [Source](https://www.gia.edu/pearl-description) · [Archived copy](https://web.archive.org/web/20261017085317/https://www.gia.edu/pearl-description) **Written by:** Learn About Pearls editors **Fact-checked:** Learn About Pearls editors, October 26, 2026 **Reviewed by:** Simon, October 26, 2026 **First published:** November 4, 2026 **Publisher:** [Unique Pearl](https://learnaboutpearls.com/about/), a pearl jeweler **Revision history** 1. November 4, 2026: First published. First published **How to cite this page** **APA:** Learn About Pearls editors. (2026). _What Size Pearls Should You Choose?_ Learn About Pearls. https://learnaboutpearls.com/buying/pearl-size-guide/ **MLA:** “What Size Pearls Should You Choose?” _Learn About Pearls_, Unique Pearl, November 4, 2026, learnaboutpearls.com/buying/pearl-size-guide/. **Chicago:** Learn About Pearls editors. “What Size Pearls Should You Choose?” Learn About Pearls. Unique Pearl. Last modified November 4, 2026. https://learnaboutpearls.com/buying/pearl-size-guide/. **BibTeX:** `@misc{lap-buying-pearl-size-guide, title = {What Size Pearls Should You Choose?}, author = {{Learn About Pearls editors}}, year = {2026}, howpublished = {\url{https://learnaboutpearls.com/buying/pearl-size-guide/}}, note = {Learn About Pearls, published by Unique Pearl}}` Quoting with attribution and a link is welcome. See [how to cite and reuse](https://learnaboutpearls.com/cite/). **Suggest a correction** ## Related pages - [Buying](https://learnaboutpearls.com/buying/): How to compare pearl types and quality, what to ask a seller, and when to get a lab report. - [Necklace lengths](https://learnaboutpearls.com/buying/necklace-lengths/): The seven standard necklace lengths, collar to rope, in centimeters and inches. - [Pearl types](https://learnaboutpearls.com/types/): Akoya, freshwater, South Sea, Tahitian and keshi pearls, and where each one comes from.