Century and millennium calculator
Enter a year to get its correct century number, such as 1995 being in the 20th century and 2026 in the 21st, a common homework question.
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How to use it
- Enter year.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
There is no year zero, so the 1st century runs from 1 to 100. Century = ceiling(year ÷ 100), from (century - 1) × 100 + 1 to century × 100. Millennium = ceiling(year ÷ 1000). Decade = floor(year ÷ 10) × 10.
Example
Inputs: Year = 2,026. Result: Century: 21st century; Century span: 2001-2100; Year within the century: 26.
Limits and caveats
- It uses the strict count where a century starts in a year ending in 01, although many people celebrate the new century in the year ending in 00.
- The decade uses the popular 0 to 9 grouping, unlike the strict century count.
Questions about this tool
What century are we in now?
The 21st century, which began on 1 January 2001 and ends on 31 December 2100.
Is 2000 in the 20th or 21st century?
By the strict count it is the last year of the 20th century, because the 1st century began in year 1 as there is no year zero.
Why is 1995 in the 20th century, not the 19th?
The 19th century covers 1801 to 1900, so years that start with 19 mostly fall in the 20th century.