Rarest SI Prefix — All 24 Answers Ranked by Rarity
24 answers are accepted for “Name an SI prefix”. Ronto- is the rarest SI prefix in this ranking, with 725 monthly Wikipedia views (rarity 1.000, Legendary). Zepto- is the second-rarest with 1,238 monthly Wikipedia views, 1.71× the figure for Ronto-. Micro- is the most common SI prefix in this ranking, with 80,943 monthly Wikipedia views, 111.6× the figure for the rarest. Combined monthly Wikipedia views across the 24 answers: 311,225. Ronto- is 0.2% of that total. 5 answers are Epic or Legendary: Ronto- (Legendary), Zepto- (Legendary), Yocto- (Epic), and 2 more.
Quick answer
Monthly English Wikipedia pageviews. Source: Wikidata + Wikipedia pageviews (2026-10).
Ranked answers
| Rank | Answer | Tier | Rarity | Monthly Wikipedia views |
|---|---|---|---|---|
| 1 | Ronto- on Wikipedia | Legendary | 1.000 | 725 |
| 2 | Zepto- on Wikipedia | Legendary | 0.957 | 1,238 |
| 3 | Yocto- on Wikipedia | Epic | 0.913 | 1,406 |
| 4 | Zetta- on Wikipedia | Epic | 0.870 | 1,657 |
| 5 | Quecto- on Wikipedia | Epic | 0.826 | 1,771 |
| 6 | Pico- on Wikipedia | Rare | 0.783 | 1,836 |
| 7 | Exa- on Wikipedia | Rare | 0.739 | 2,379 |
| 8 | Peta- on Wikipedia | Rare | 0.696 | 2,425 |
| 9 | Femto- on Wikipedia | Rare | 0.652 | 2,490 |
| 10 | Ronna- on Wikipedia | Rare | 0.609 | 2,528 |
| 11 | Atto- on Wikipedia | Uncommon | 0.565 | 3,787 |
| 12 | Yotta- on Wikipedia | Uncommon | 0.522 | 4,059 |
| 13 | Quetta- on Wikipedia | Uncommon | 0.478 | 4,104 |
| 14 | Centi- on Wikipedia | Uncommon | 0.435 | 5,559 |
| 15 | Deca- on Wikipedia | Familiar | 0.391 | 9,925 |
| 16 | Hecto- on Wikipedia | Familiar | 0.348 | 10,049 |
| 17 | Milli- on Wikipedia | Familiar | 0.304 | 11,321 |
| 18 | Tera- on Wikipedia | Familiar | 0.261 | 13,789 |
| 19 | Giga- on Wikipedia | Familiar | 0.217 | 23,063 |
| 20 | Mega- on Wikipedia | Common | 0.174 | 25,308 |
| 21 | Kilo- on Wikipedia | Common | 0.130 | 29,737 |
| 22 | Deci- on Wikipedia | Common | 0.087 | 31,467 |
| 23 | Nano- on Wikipedia | Common | 0.043 | 39,659 |
| 24 | Micro- on Wikipedia | Common | 0.000 | 80,943 |
FAQ
What is the rarest SI prefix?
Ronto- is the rarest SI prefix in this ranking, with 725 monthly Wikipedia views (rarity 1.000, Legendary).
How many SI prefixes are there?
There are 24 SI prefixes in this ranking, from Ronto- (rarest) to Micro- (most common).
What is the most common SI prefix?
Micro- is the most common SI prefix in this ranking, with 80,943 monthly Wikipedia views (Common).
Play
Unlimited mode uses this prompt. A rarer correct answer scores more.
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Sources
Recorded source: Wikidata + Wikipedia pageviews (2026-10). The answer list is compiled from Wikidata (CC0), and the view counts are monthly English Wikipedia pageviews. Rarity is the percentile of the popularity figure inside this prompt: 1 is the rarest and 0 is the most common. Linked names open the English Wikipedia article stored on that answer.