What is a sextillion?

A sextillion is the number 1,000,000,000,000,000,000,000 — a one followed by twenty-one zeros. It equals one thousand quintillions. Numbers of this magnitude are encountered in particle physics (the estimated number of stars in the observable universe is on the order of sextillions) and in certain molecular-count calculations in chemistry, such as multiples of Avogadro's number.

Twenty-one zeros are far beyond what anyone can count reliably by hand. At this scale, manually writing out the full number is impractical without a tool that handles the zero-padding automatically.

Tool description

This tool converts numbers expressed in sextillions to their full numeric form and vice versa. Type a value in the "Sextillions" field and see it expanded with all twenty-one zeros, or enter a massive number in the "Full Number" field to learn how many sextillions it represents. The conversion is bidirectional and instant.

Examples

Sextillions Full Number
1 1000000000000000000000
2 2000000000000000000000
0.5 500000000000000000000
7.3 7300000000000000000000
0.001 1000000000000000000

Features

  • Instant bidirectional conversion between sextillions and full numbers
  • Handles decimal values accurately with string-based math
  • No floating-point precision loss regardless of number size
  • Runs entirely in the browser with immediate results
  • One-click swap to reverse the conversion direction

Use cases

  • Expressing star counts or particle estimates in astrophysics and chemistry
  • Writing out large molecular quantities for scientific publications
  • Converting shorthand numbers in theoretical physics discussions
  • Quintillion Number Converter — for numbers with 18 zeros
  • Septillion Number Converter — for numbers with 24 zeros