"How many millions in a billion" is the question a child asks when the news says a company is worth 2 billion and last week's homework was in millions, and the question an adult asks when moving money, data or population figures between units. The answer is a thousand, and the whole ladder works the same way: thousand, million, billion, trillion, each a thousand times the last. This page has the conversion table both ways, the method for converting any figure, the Indian lakh and crore equivalents (which many families need daily), how the commas differ, how to write the numbers in words and in scientific notation, and what each size is as big as. The printable has the tables and practice on two pages.
Download the million-billion-trillion conversion table with lakh and crore (PDF) (the conversion table both ways, the Indian equivalents with the comma positions, the words and scientific notation column, what each size is as big as, and twelve practice questions with answers; two pages, free).
The answer, and the ladder
| Digits | Zeros | Equals | |
|---|---|---|---|
| thousand | 1,000 | 3 | 1,000 ones |
| million | 1,000,000 | 6 | 1,000 thousands |
| billion | 1,000,000,000 | 9 | 1,000 millions |
| trillion | 1,000,000,000,000 | 12 | 1,000 billions |
So there are 1,000 millions in a billion, 1,000 billions in a trillion, and 1,000 × 1,000 = 1,000,000 millions in a trillion. Each step up the ladder adds three zeros, which is one more comma group.
The conversion table both ways
| From \ To | thousand | million | billion | trillion |
|---|---|---|---|---|
| 1 thousand = | 1 | 0.001 | 0.000001 | 0.000000001 |
| 1 million = | 1,000 | 1 | 0.001 | 0.000001 |
| 1 billion = | 1,000,000 | 1,000 | 1 | 0.001 |
| 1 trillion = | 1,000,000,000 | 1,000,000 | 1,000 | 1 |
To convert any amount: going up the ladder (millions to billions) divide by 1,000 for each step; going down (billions to millions) multiply by 1,000 for each step. Moving the decimal point three places does the same job.
| The figure | The working | The answer |
|---|---|---|
| 2.5 billion in millions | 2.5 × 1,000 | 2,500 million |
| 350 million in billions | 350 ÷ 1,000 | 0.35 billion |
| 7 trillion in billions | 7 × 1,000 | 7,000 billion |
| 7 trillion in millions | 7 × 1,000 × 1,000 | 7,000,000 million |
| 45,000 million in billions | 45,000 ÷ 1,000 | 45 billion |
| 0.8 billion in thousands | 0.8 × 1,000 × 1,000 | 800,000 thousand |
| 1.4 billion people in millions | 1.4 × 1,000 | 1,400 million |
In lakh and crore
Indian English groups large numbers in a different way, and the commas show it: after the first three digits, every two digits get a comma.
| Indian | Digits (Indian commas) | International | Digits (international commas) |
|---|---|---|---|
| 1 lakh | 1,00,000 | 100 thousand | 100,000 |
| 10 lakh | 10,00,000 | 1 million | 1,000,000 |
| 1 crore | 1,00,00,000 | 10 million | 10,000,000 |
| 10 crore | 10,00,00,000 | 100 million | 100,000,000 |
| 100 crore (1 arab) | 1,00,00,00,000 | 1 billion | 1,000,000,000 |
| 1,000 crore | 10,00,00,00,000 | 10 billion | 10,000,000,000 |
| 1 lakh crore | 1,00,00,00,00,00,000 | 1 trillion | 1,000,000,000,000 |
The four facts to memorise: 1 million = 10 lakh; 1 crore = 10 million; 1 billion = 100 crore; 1 trillion = 1 lakh crore. To go from crore to million multiply by 10; from million to crore divide by 10; from crore to billion divide by 100. A salary of 1.2 crore rupees a year is 12 million rupees; a company valued at 5 billion dollars is worth 500 crore dollars. The commas are the usual slip when a child educated in one system writes for a school in the other: 25,00,000 and 2,500,000 are the same number (25 lakh, 2.5 million).
Writing big numbers in words and in scientific notation
| Digits | In words | Scientific notation |
|---|---|---|
| 4,000,000 | four million | 4 × 10^6 |
| 4,500,000 | four million five hundred thousand (4.5 million) | 4.5 × 10^6 |
| 2,000,000,000 | two billion | 2 × 10^9 |
| 2,300,000,000 | two billion three hundred million (2.3 billion) | 2.3 × 10^9 |
| 7,000,000,000,000 | seven trillion | 7 × 10^12 |
| 7,250,000,000,000 | seven trillion two hundred fifty billion (7.25 trillion) | 7.25 × 10^12 |
In scientific notation the power of ten counts the places the decimal point moved: 2,300,000,000 becomes 2.3 with the point moved 9 places, so 2.3 × 10^9. The names of the steps beyond trillion (quadrillion, quintillion and so on) are on the what comes after trillion page.
What a million, a billion and a trillion are as big as
| Seconds | Days | Dollars at $1,000 a day | Stacked $100 bills | |
|---|---|---|---|---|
| million | 11.6 days | 2,740 years | 2.7 years | about 1 metre |
| billion | 31.7 years | 2.7 million years | 2,740 years | about 1 kilometre |
| trillion | 31,700 years | 2.7 billion years | 2.7 million years | about 1,000 kilometres |
The seconds column is the one children remember: a million seconds ago was last week, a billion seconds ago was before the internet, and a trillion seconds ago people were painting caves. Population gives another sense: the United States has about 340 million people, India and China about 1.4 billion each, and the world about 8.1 billion; there has never been a trillion people alive at once or in all of history.
The old British billion
Until 1974 British English used the long scale: a billion was a million million (10^12) and a thousand million was called a milliard. The UK government switched to the American short scale that year, and every British newspaper, textbook and bank now uses billion for a thousand million. Old books, and the modern usage in German (Milliarde, Billion), French (milliard, billion), Spanish (mil millones, billón), Italian and Dutch, still follow the long scale, so a German Billion is an English trillion. A number written in digits or as a power of ten means the same everywhere.
Practice: twelve questions
- How many millions in 6 billion?
- How many billions in 4,500 million?
- Write 3.2 billion in millions.
- Write 750 million in billions.
- How many millions in a trillion?
- How many lakh in 3 million?
- How many crore in 2 billion?
- Write 45 crore in millions.
- Write 1,20,00,000 with international commas and in words.
- Write 2.75 billion in scientific notation.
- A country's debt is 1.5 trillion dollars. How many billion is that?
- A city of 8 million people: how many lakh?
Answers: 1) 6,000 million. 2) 4.5 billion. 3) 3,200 million. 4) 0.75 billion. 5) 1,000,000. 6) 30 lakh. 7) 200 crore. 8) 450 million. 9) 12,000,000, twelve million (1.2 crore). 10) 2.75 × 10^9. 11) 1,500 billion. 12) 80 lakh.
Download the million-billion-trillion conversion table with lakh and crore (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 and CBSE, including children moving between the Indian and international systems: place value with the comma groups written out on the shared screen, converting between units of a thousand, and scientific notation for the older ones. 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
1How many millions are in a billion?
2How many millions are in a trillion?
3How many crore is a billion?
4How much is a billion dollars?
5Is a billion 100 million or 1,000 million?
See how we teach this, 1-on-1 online →
Shobha
Founder and lead tutor, Science with Shobha
Teaching maths, science and English to children online since 2018. 500+ students, 20+ tutors, families in nine countries.