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How big is a googol? Naming huge numbers

Everyone knows million, billion and trillion. But the naming keeps going far past the point where the numbers mean anything to us — all the way to a googol and beyond. Here is how those names are built, in plain English, and just how staggeringly large they get.

The familiar ladder

Counting up in thousands gives us the everyday names: a thousand is 1,000 (10³), a million is a thousand thousand (10⁶), a billion is a thousand million (10⁹), and a trillion is a thousand billion (10¹²). Each new name adds three more zeros. That pattern — multiply by a thousand, get the next name — is the whole trick, and it continues indefinitely.

Why "billion" is secretly ambiguous

There are actually two naming systems, and they disagree. The short scale — standard today in the United States and modern Britain — makes each new -illion a thousand times the last, so a billion is 10⁹. The older long scale, still used in much of continental Europe, makes each new -illion a million times the last, so a billion there is 10¹² and the number 10⁹ gets its own name, a milliard. It is the same word, "billion", pointing at two different numbers — which is exactly why careful writers sometimes prefer to just write the digits.

The -illions in order (short scale)

Past a trillion the names carry on with Latin-derived prefixes. Each step adds three zeros:

• Quadrillion — 10¹⁵
• Quintillion — 10¹⁸
• Sextillion — 10²¹
• Septillion — 10²⁴
• Octillion — 10²⁷
• Nonillion — 10³⁰
• Decillion — 10³³
• …continuing to a centillion, which is 10³⁰³ on the short scale.

The prefixes are just Latin counting words — quad (4), quint (5), sext (6) — describing which step of the ladder you are on. Mathematicians have formal systems (the Conway–Wechsler naming scheme is the best known) for extending this to arbitrarily large -illions, so in principle every number on the ladder has a name.

Enter the googol

A googol is a 1 followed by 100 zeros — that is 10¹⁰⁰. It was named in 1938 not by a mathematician but by a nine-year-old: Milton Sirotta, the nephew of mathematician Edward Kasner, who was asked to invent a word for a ridiculously big number. The name later inspired the spelling of a certain search engine.

A googol is not just "a lot". It is larger than the number of atoms in the observable universe, which is estimated at somewhere around 10⁸⁰. So a googol exceeds the count of every atom in everything we can see by a factor of roughly 10²⁰ — a hundred billion billion times over. There is no physical quantity in the known universe that reaches a googol.

The googolplex, and numbers that dwarf it

If a googol is 10¹⁰⁰, a googolplex is 10 raised to the power of a googol — a 1 followed by a googol of zeros. You could not write it out even if you used every atom in the universe as an inkwell; there is not enough room in the cosmos for the digits. And yet it is still nowhere near "the biggest number", because there is no biggest number — you can always add one.

Beyond the googolplex, mathematicians work with quantities so vast that the -illion naming scheme gives up entirely. Famous examples like Graham's number are so large they need their own special notation just to be described at all, let alone written down. The lesson of the very large is a humbling one: our intuition runs out long, long before the numbers do.

Frequently asked questions

Related guide: googolplex vs infinity — why big isn't "almost infinite". Or browse all the guides.