The direct answer
A quadrillion has 15 zeros: 1,000,000,000,000,000 = 1015.
A quadrillion is 1,000 trillion. The prefix quad- helps show that it is the fourth “illion” step: million, billion, trillion, quadrillion.
See the zeros in groups of three
Start with the 1 and count the zero groups to its right. Each complete group contributes three zeros, so 5 groups × 3 zeros = 15 zeros.
Previous and next named numbers
| Position | Name | Written number | Power |
|---|---|---|---|
| Previous | trillion | 1,000,000,000,000 | 1012 |
| Current | quadrillion | 1,000,000,000,000,000 | 1015 |
| Next | quintillion | 1,000,000,000,000,000,000 | 1018 |
Each move to the right multiplies the number by 1,000 and adds three zeros.
How to say and write quadrillion
The number 1,000,000,000,000,000 is written in words as one quadrillion. A number such as 2,000,000,000,000,000 is two quadrillion; the scale word itself does not become plural inside a number name.
Short-scale note: Big Number Playground uses the modern English short scale, where billion is 109 and each new “illion” is 1,000 times the previous one.
Explore related large numbers
Use the Big Number Explorer to convert any whole number to words, or continue with the large number names chart and the million, billion and trillion comparison.