Age Calculator — Step-by-Step Solutions

The Age Calculator determines your exact age from your date of birth, broken down into years, months, days, and even total hours and minutes. It also detects your zodiac sign and shows your next birthday countdown.

Two modes are available: calculate your age from a birth date, or find the number of days between any two dates. Results include both precise breakdowns and fun facts about your age.

Date of Birth

Your calculations will appear here

How to Use the Age Calculator

Age from Date of Birth: pick your date of birth with the date field. The calculator compares it with today and shows your age in years, months and days, plus total days, weeks, hours and minutes lived, the day you were born on, days until your next birthday and your zodiac sign.
Days Between Dates: choose a start date and an end date. The order does not matter. You get the difference in days, weeks plus days, hours, an exact years-months-days difference and approximate months and years.
For a deadline or countdown, set the start date to today and the end date to the target date.
The date field uses your device format. The result is based on calendar dates, so time zones and clock times are ignored.

Formula and Theory

Age is counted in completed calendar units. You turn a year older on the day that matches your birth month and day, not after 365 days, because leap years add an extra day about every fourth year. That is why total days divided by 365 can differ slightly from your age in years.

The year-month-day breakdown works by subtraction with borrowing, as in column subtraction. Subtract the birth year, month and day from the current ones. If the days come out negative, borrow the length of the previous month and reduce the months by one; if the months come out negative, borrow 12 months from the years.

The number of days between two dates is the difference of the two calendar dates, counting each midnight to midnight. The start date is not counted and the end date is, so 1 March to 2 March is 1 day. Weeks are days divided by 7, with the leftover days reported separately.

Months are not equal in length, so a duration given in months and days depends on the starting date. For exact lengths, use the day count.

Worked Examples

Example 1: Age in years, months and days

Problem: Someone was born on 15 March 1990. What is their age on 10 August 2024?

Solution: Subtract year, month and day: 2024 - 1990 = 34 years, 8 - 3 = 5 months, 10 - 15 = -5 days. The days are negative, so borrow July, which has 31 days: days = -5 + 31 = 26 and months = 5 - 1 = 4.

Answer: 34 years, 4 months, 26 days

Example 2: Days and weeks between two dates

Problem: How long is it from 1 January 2000 to 15 March 2024?

Solution: From 1 January 2000 to 1 January 2024 is 24 years, which contains 6 leap days (2000, 2004, 2008, 2012, 2016, 2020), so 24 x 365 + 6 = 8,766 days. From 1 January to 15 March 2024 adds 31 + 29 + 14 = 74 days (2024 is a leap year). Total = 8,766 + 74 = 8,840 days, which is 1,262 weeks and 6 days (1,262 x 7 = 8,834). The calendar breakdown is 24 years, 2 months, 14 days.

Answer: 8,840 days = 1,262 weeks and 6 days

Example 3: A countdown

Problem: How many days from 15 January 2025 to 1 March 2025?

Solution: Days left in January after the 15th: 31 - 15 = 16. Add all of February (28 days in 2025): 16 + 28 = 44. Add 1 for 1 March: 45.

Answer: 45 days (6 weeks and 3 days)

Example 4: Total days lived

Problem: Using the same birth date, 15 March 1990, how many days had passed by 10 August 2024?

Solution: Count whole years first: 15 March 1990 to 15 March 2024 is 34 years. The leap days in that span are 29 February of 1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020 and 2024, which is 9, so 34 x 365 + 9 = 12,419 days. From 15 March to 10 August 2024: 16 (rest of March) + 30 + 31 + 30 + 31 + 10 = 148 days. Total = 12,419 + 148 = 12,567 days, which is 1,795 weeks.

Answer: 12,567 days (1,795 weeks)

Frequently Asked Questions

How is age calculated from a date of birth?

Subtract the birth date from the current date year by year, month by month and day by day, borrowing from the previous unit when a part is negative. The calculator does this and also gives the total number of days.

Does the calculator account for leap years?

Yes. It uses real calendar dates, so the extra day in a leap year is included in totals of days, weeks and hours.

How many days are there between two dates?

Choose them in the Days Between Dates mode. The result counts the days from the start date up to and including the end date, so the difference between consecutive days is 1.

Why is my age in days not exactly my years times 365?

Each leap year adds a day, so over 30 years about 7 or 8 extra days appear. Total days will be slightly above years x 365.

What is the zodiac sign based on?

Only your birth day and month, using the usual western date ranges for each sign. It is shown for interest and has no effect on the age result.

Can I calculate age on a future or past date?

Use Days Between Dates with your birth date as the start and the target date as the end. The Exact Difference line gives the age in years, months and days on that date.