What comes after trillion? Quadrillion, then quintillion, sextillion, septillion and on to vigintillion and centillion: the names of large numbers with their zeros and powers of ten, how the names are built, the short scale against the long scale (why a British billion used to be a million million), googol and googolplex, the SI prefixes from kilo to quetta, the Indian lakh-crore names, and a printable table

"What comes after trillion" is asked by children who have just learned that million, billion and trillion are a thousand times each other and want to know how far the ladder goes, and by adults checking a news figure. The ladder goes a long way: the names are built by a rule, so there is a name for every group of three zeros up to centillion, and beyond that there are a few famous inventions. This page has the full table with zeros and powers of ten, the rule that makes the names, the two scales (the reason a British billion once meant something different), the SI prefixes, the Indian system, and what each size is as big as. The printable has the table on one page and the scales, prefixes and practice on the other.

Download the names of large numbers table (PDF) (every -illion from thousand to centillion with its zeros and power of ten, the short-scale and long-scale comparison, the SI prefixes to quetta, the Indian lakh-crore names, what each size is as big as, and ten practice questions with answers; two pages, free).

The answer

After trillion comes quadrillion: 1,000,000,000,000,000, a 1 with 15 zeros, written 10^15. Then quintillion (18 zeros), sextillion (21), septillion (24), octillion (27), nonillion (30) and decillion (33). Each name is a thousand times the one before, so the zeros go up in threes.

The table: thousand to centillion

Between vigintillion (63 zeros) and centillion (303 zeros) the names continue by the same rule (trigintillion 10^93, quadragintillion 10^123, quinquagintillion 10^153 and so on), but almost nobody uses them; scientists write 10^93 instead.

How the names are built

Every name is Latin for its position on the ladder. Bi-llion is the second step after million, tri-llion the third, quadr-illion the fourth, quint-illion the fifth, then sext, sept, oct, non, dec for six to ten. In the short scale the n-th -illion equals 10^(3n + 3): billion is n = 2, so 10^9; trillion is n = 3, so 10^12; decillion is n = 10, so 10^33. The names from eleven onwards bolt a units word onto "dec": un-dec-illion (11), duo-dec-illion (12), tre-dec-illion (13); vigintillion is twenty (10^63) and centillion is a hundred (10^303).

The quick way to find the zeros of any -illion: take its number, multiply by three, add three. Septillion is the seventh: 7 × 3 + 3 = 24 zeros.

Short scale and long scale

There are two systems in the world, and they disagree from a billion upwards.

In the short scale each name is a thousand times the last; in the long scale each -illion is a million times the last, with a -illiard (milliard, billiard) for the thousand steps in between. British English used the long scale until 1974, when the government adopted the short scale for official statistics, which is why an old British encyclopaedia says a billion is a million million while a new one says a thousand million. A family whose children are at school in Germany, France or the Netherlands meets the long scale in class: a German Billion is an English trillion. A sum written in digits or in powers of ten is the same everywhere, which is why science uses 10^12 and not the word.

The SI prefixes: the same ladder on units

Units use prefixes instead of names, and since 2022 the ladder reaches 10^30.

Ronna and quetta were added by the General Conference on Weights and Measures in November 2022, the first new prefixes since 1991. A terabyte hard drive holds a trillion bytes; a petabyte is a thousand of those.

The Indian system

Indian English counts in a different grouping above a thousand, and the commas move with it:

A million is ten lakh; a billion is a hundred crore; a trillion is a lakh crore. The million-billion-trillion conversion page has the full table both ways.

What each size is as big as

Numbers this large only mean something next to a real quantity. These are rounded, well-known estimates:

Practice: ten questions

1. How many zeros in a quadrillion?
2. How many millions in a billion?
3. How many billions in a trillion?
4. Write 3 × 10^9 in words (short scale).
5. Which is bigger, 10^15 or a quintillion?
6. What is the 8th -illion called, and how many zeros does it have?
7. A German newspaper says a company is worth "2 Billionen Euro". How much is that in English?
8. Write 1 crore in short-scale words.
9. Write 5,000,000,000,000 as a power of ten times a single digit.
10. How many zeros does a googol have?

Answers: 1) 15. 2) 1,000. 3) 1,000. 4) three billion. 5) A quintillion (10^18). 6) Octillion, 27 zeros (8 × 3 + 3). 7) 2 trillion euros. 8) ten million. 9) 5 × 10^12 (five trillion). 10) 100.

Download the names of large numbers table (PDF)

Where to get help

A 1-on-1 online maths class with a tutor who holds a master's in mathematics, for grades 3 to 8 in the US curriculum and the equivalent years in England, Australia, the Netherlands and CBSE: place value and large numbers with the comma groups written out on the shared screen, powers of ten and scientific notation for the older children, and the Indian and European systems for families who move between them. The recording and notes after every class, the same tutor every week, US$10 to $13 an hour. The grade 6 math page has the grades; the free 30-minute first class is a real lesson, usually on the homework the child brings.

Questions parents ask

See how we teach this, 1-on-1 online →