Century — Definition, Formula & Examples
A century is a unit of time equal to 100 years. It is commonly used in history, everyday language, and math word problems involving long spans of time.
A century is a standard unit of time measurement defined as a period of exactly 100 consecutive years.
Key Formula
Where:
Worked Example
Problem: The Great Wall of China was built over a period of about 2,000 years. How many centuries is that?
Set up the conversion: Divide the total number of years by 100, since 1 century equals 100 years.
Answer: 2,000 years is equal to 20 centuries.
Why It Matters
Understanding centuries helps you solve word problems that involve converting between years and larger time units. It also builds a foundation for working with unit conversions in measurement topics throughout elementary and middle school math.
Common Mistakes
Mistake: Confusing which century a year belongs to. For example, thinking the year 1999 is in the 19th century.
Correction: The years 1901–2000 make up the 20th century, not the 19th. The century number is always one more than the leading digits for years after the year 100.