How Many Zeros in a Quadrillion?
A quadrillion has 15 zeros: 1,000,000,000,000,000. In scientific notation it is written as 1015. The short-scale system — used in the United States and modern British English — defines a quadrillion as one thousand trillion. This number has five groups of three zeros beyond the initial 1, which is why counting the zeros manually can be a useful double-check. The prefix quadri- means four, referring to the fourth power of a million (106×4 = 1024) in the older long-scale system, though in everyday modern usage a quadrillion always means 1015. Learn more about trillion zeros.
A quadrillion has
15
zeros
- Written Form
- 1 followed by 15 zeros
- Scientific
- 10¹⁵
How Many Zeros Separate a Quadrillion from a Trillion?
A quadrillion is exactly 1,000 times larger than a trillion. A trillion has 12 zeros; a quadrillion has 15 — three additional zeros representing that factor of one thousand. To put that step in perspective: if a trillion seconds is roughly 31,700 years, then a quadrillion seconds is closer to 31.7 million years.
The jump from trillion to quadrillion follows the same pattern that applies across the entire short-scale sequence: each successive name adds three more zeros. Quintillion comes next with 18 zeros, and the pattern continues from there. The table below shows where quadrillion sits in that sequence: Learn more about how many zeros does a decillion have.
| Name | Zeros | Written out |
|---|---|---|
| Trillion | 12 | 1,000,000,000,000 |
| Quadrillion | 15 | 1,000,000,000,000,000 |
| Quintillion | 18 | 1,000,000,000,000,000,000 |
Real-world references at the quadrillion scale include global financial figures. The total notional value of global derivatives markets has been estimated in the hundreds of trillions to low quadrillions of dollars. The number of cells in the human body is also sometimes quoted near the quadrillion range when counting cellular organisms in the microbiome.
How Many Zeros Does a Long-Scale Quadrillion Have?
In the long-scale numbering system — historically used in much of continental Europe and still official in many countries — a quadrillion means something very different: 1024, or 1 followed by 24 zeros. This is because the long scale defines each new "-illion" as a million times the previous one, rather than a thousand times. Learn more about how many zeros does a billion have.
So a long-scale quadrillion equals what the short scale calls a septillion. This gap grows wider with each step up the naming ladder, which is why scientific papers and international finance use scientific notation rather than number names — 1015 means the same thing everywhere, regardless of which naming convention a reader uses. Related: Million zeros.
For practical purposes, if you are reading an English-language source published in the US or UK after the 1970s, "quadrillion" almost certainly refers to 15 zeros (1015). The long-scale meaning has largely faded from everyday English use.