How Many Zeros in a Octillion?
An octillion has 27 zeros: 1,000,000,000,000,000,000,000,000,000. In scientific notation, the number of zeros in an octillion is expressed as 1027. 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. One octillion equals one thousand septillion (1024), following the same pattern that applies throughout the short-scale sequence — each named number adds three zeros to the previous one. The SI unit prefix for 1027 is ronna-, added to the International System of Units in 2022 precisely because data storage and physics were reaching this scale. Learn more about trillion zeros.
A octillion has
27
zeros
- Written Form
- 1 followed by 27 zeros
- Scientific
- 10²⁷
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:
| Name | Zeros | Scientific Notation |
|---|---|---|
| Septillion | 24 | 1024 |
| Octillion | 27 | 1027 |
| Nonillion | 30 | 1030 |
To verify the zero count in an octillion, 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. Alternatively, in scientific notation 1027, the exponent directly tells you how many zeros follow the leading 1. See also: How many zeros in a trevigintillion.
At the octillion scale, quantities appear in atomic and nuclear physics. The estimated number of atoms in a human body is around 7 × 1027 — about seven octillion atoms. This makes the octillion one of the first numbers in the sequence that shows up in serious scientific measurements rather than purely abstract mathematics.
How Many Zeros Does the Long-Scale Octillion Have?
In the long-scale numbering system — used historically in much of 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. Learn more about zeros in an octodecillion.
This means the long-scale octillion is 1021 times larger than the short-scale octillion — a difference of a sextillion (1021). For practical purposes in English-language science and finance, "octillion" always refers to 1027 and 27 zeros. If you encounter octillion in older European-published texts, verify which convention the source uses.