What is a quintillion?

A quintillion is the number 1,000,000,000,000,000,000 — a one followed by eighteen zeros. It equals one thousand quadrillions or one million trillions. Quintillions are used in fields such as cryptography, where the number of possible encryption keys can reach quintillion-scale, and in astronomy, where distances measured in meters between stars easily exceed quintillions.

Eighteen zeros are virtually impossible to count reliably by eye. Even careful manual entry is likely to produce off-by-one-zero errors, which represent a thousand-fold difference. An automated converter is the only practical way to work with numbers this large.

Tool description

This tool converts numbers expressed in quintillions to their full numeric form and vice versa. Enter a value in the "Quintillions" field to see it written out with all eighteen zeros, or paste a long number into the "Full Number" field to find out how many quintillions it contains. The conversion is bidirectional and updates in real time.

Examples

Quintillions Full Number
1 1000000000000000000
4.6 4600000000000000000
0.1 100000000000000000
10 10000000000000000000
0.005 5000000000000000

Features

  • Instant bidirectional conversion between quintillions and full numbers
  • Precise decimal handling (e.g. 2.5 quintillion → 2500000000000000000)
  • String-based decimal shifting ensures zero floating-point errors
  • No server calls — works entirely in the browser
  • One-click swap to reverse the conversion direction

Use cases

  • Working with encryption key spaces in cybersecurity documentation
  • Expressing astronomical distances or particle counts in full form
  • Converting large-scale data metrics in physics and engineering
  • Quadrillion Number Converter — for numbers with 15 zeros
  • Sextillion Number Converter — for numbers with 21 zeros