How to work out 100 years in days
Multiply the years by 365, then add one day for every February 29 between the birth date and the 100th birthday. Leap years come every four years, except century years not divisible by 400, so a 100-year span covers exactly 25 of them.
100 years in days
100 × 365 = 36,500 days
+ 25 leap days
= 36,525 days
+ 25 leap days
= 36,525 days
Exact days at the 100th birthday
Examples for different birth years. The total changes slightly depending on which leap years fall inside the span.
| Born | 100th birthday | Days old |
|---|---|---|
| January 1, 1940 | Sunday, January 1, 2040 | 36,525 |
| January 1, 1950 | Saturday, January 1, 2050 | 36,525 |
| January 1, 1960 | Thursday, January 1, 2060 | 36,525 |
| January 1, 1970 | Wednesday, January 1, 2070 | 36,525 |
| January 1, 1980 | Monday, January 1, 2080 | 36,525 |
| January 1, 1990 | Sunday, January 1, 2090 | 36,525 |
100 years in other units
| Unit | 100 years is |
|---|---|
| Months | 1,200 |
| Weeks | about 5,217 |
| Days | 36,525 |
| Hours | about 876,576 |
| Minutes | about 52,594,560 |
| Seconds | about 3,155,673,600 |
Calculate your exact age in days
Enter your birthday to see how many days old you are.
For age in years, months and days, use the Age Calculator.