How Many Zeros in a Petabyte?
A petabyte (PB) has 15 zeros in the decimal system: 1,000,000,000,000,000 bytes, or 1015 bytes. One petabyte equals 1,000 terabytes or one quadrillion bytes. This is the definition used by storage manufacturers and the SI standard. The binary equivalent — a pebibyte (PiB) — equals 250 = 1,125,899,906,842,624 bytes, roughly 12.6% larger than the decimal petabyte. The prefix "peta-" traces back to the Greek word for five, reflecting petabyte's position as the fifth step up the SI storage scale from a single byte. Related: How many zeros does a byte have.
A petabyte has
15
zeros
- Written Form
- 1 followed by 15 zeros bytes
- Scientific
- 10¹⁵ bytes
- Binary (IEC)
- 2⁵⁰ bytes (PiB)
How Many Zeros Are in a Petabyte?
In the decimal system, 1 PB = 1,000,000,000,000,000 bytes — exactly 15 zeros after the leading 1. The exponent in 1015 gives you that count directly. This is the same number of zeros as one quadrillion, which makes sense because a petabyte is literally one quadrillion bytes. See also: Gigabyte zeros.
In binary, the pebibyte (PiB) equals 250 bytes, which is not a round number and has no clean trailing-zero count. The table below compares both definitions:
| Unit | Bytes | Zeros | Notation |
|---|---|---|---|
| Petabyte (decimal, SI) | 1,000,000,000,000,000 | 15 | 1015 |
| Pebibyte (binary, IEC) | 1,125,899,906,842,624 | — | 250 |
The 12.6% gap between the two is why a drive labeled "1 PB" may report slightly less capacity in an operating system that measures in binary units.
What Can You Store in a Petabyte?
A petabyte is an enormous amount of storage — well beyond anything a typical consumer or small business would encounter. To put it in practical terms:
- Roughly 13 years of continuous HD video streaming
- About 200 million high-resolution photos (at 5 MB each)
- Approximately 500 million pages of plain text
- Around 500,000 hours of standard-definition video
At the petabyte scale, storage becomes the domain of large enterprises, cloud providers, and research institutions. Facebook, for example, processes several petabytes of new data every day. The Large Hadron Collider at CERN generates around 15 petabytes of data annually from its particle collision experiments. Related: Yottabyte zeros.
How Does a Petabyte Compare to a Terabyte?
One petabyte equals exactly 1,000 terabytes in the decimal system. Since a modern consumer hard drive holds 1–4 TB, a single petabyte would require hundreds of such drives. The table below shows how the petabyte fits into the broader storage hierarchy:
| Unit | Zeros | Bytes | Equivalent |
|---|---|---|---|
| Gigabyte (GB) | 9 | 109 | 1,000 MB |
| Terabyte (TB) | 12 | 1012 | 1,000 GB |
| Petabyte (PB) | 15 | 1015 | 1,000 TB |
| Exabyte (EB) | 18 | 1018 | 1,000 PB |
Each step up the scale adds three more zeros. A petabyte sits three zeros above a terabyte and three zeros below an exabyte — a factor of 1,000 in either direction.