How Many Zeros in an Octillion?
How many zeros in an octillion? An octillion has 27 zeros, written as 1,000,000,000,000,000,000,000,000,000 or 1027 in scientific notation. The prefix octo- means eight, referring to the eighth group of three zeros beyond the ones place in the short-scale system used in the United States and modern scientific writing. Learn more about zeros in a septillion.
An octillion has
27
zeros
- Written Form
- 1 followed by 27 zeros
- Scientific
- 10²⁷
Octillion's Position on the Short-Scale Ladder
The direct answer: exactly 27 zeros. One octillion equals one thousand septillion, following the same pattern that applies throughout the short-scale sequence — each named number adds three zeros to the previous one.
Octillion and the SI Ronna- Prefix
The SI unit prefix for 1027 is ronna-, officially added to the International System of Units in 2022 precisely because data storage and physics were reaching this scale. Learn more about zeros in a trillion.
The estimated number of atoms in a human body is around 7 × 1027 — about seven octillion atoms.
- 1 octillion = 1,000 septillion
- 1 octillion = 1 billion billion billion (109 × 109 × 109)
- 1 octillion = 1,000,000,000 quintillion
Quick Zero-Counting Trick
Count the digit groups in the written form 1,000,000,000,000,000,000,000,000,000 — there are nine groups of three digits, giving 27 zeros in total. In scientific notation, the exponent tells you the same thing directly.
How Many Zeros Are in Septillion, Octillion, and Nonillion?
Octillion sits between septillion and nonillion in the short-scale sequence. All three follow the same three-zeros-per-step pattern. Learn more about zeros in an octodecillion.
| Name | Zeros | Scientific notation |
|---|---|---|
| Septillion | 24 | 1024 |
| Octillion | 27 | 1027 |
| Nonillion | 30 | 1030 |
How Many Zeros Does the Long-Scale Octillion Have?
In the long-scale numbering system, used historically across continental Europe, an octillion represents 1048, or 1 followed by 48 zeros. The long scale defines each new "-illion" as one million times the previous, so long-scale octillion = (106)8 = 1048 — a difference of a full sextillion (1021) from the short-scale value.
Zeros in an Octillion: FAQ
What comes before an octillion?
Quick answer
Hundred septillion comes right before an octillion.
What comes after an octillion?
Quick answer
Ten octillion comes next, followed by hundred octillion and then nonillion.
How many digits does an octillion have?
An octillion has 28 digits in total — that's the digit 1 followed by 27 zeros.
How many zeros in 2 octillion? In half an octillion?
Two octillion keeps the same 27 zeros. Half an octillion has 26 trailing zeros after the 5.
Is a 27-digit number always an octillion?
No. A 27-digit number ranges up to hundreds of septillions before reaching an octillion — an octillion is the first 28-digit number.
How many zeros in an octillion in the British system?
Under the old long-scale system, an octillion meant 1048 — 21 more zeros than today's short-scale octillion. If you encounter "octillion" in older European-published texts, verify which convention the source uses.