Find your exact age in years, months and days, how long you have been alive, and when your next birthday lands.
The "as of" date starts as today. Change it to see an age on any past or future date, such as the day someone starts school or retires.
Enter a date of birth and the date you want the age measured on, which starts as today. The calculator counts every full year that has passed, then the full months left over, then the remaining days. That is the way age is stated on most official forms. It also gives your total months, weeks, days and hours lived, the weekday you were born on, and how long until your next birthday. Everything runs in your browser and nothing you enter is stored or sent anywhere.
Total days is a plain count of every calendar day between the two dates, so it includes each February 29 in between. Weeks are the total days divided by 7, rounded down. Hours are the total days times 24. Age in decimal years divides total days by 365.2425, the average length of a calendar year, which is why someone a few days past their 31st birthday shows 31.0 and change.
Take a person born on January 15, 1995, a Sunday, measured as of September 13, 2026. From January 15, 1995 to January 15, 2026 is 31 full years. From there, seven more months reaches August 15, and 29 more days reaches September 13. Their age is 31 years, 7 months and 29 days. In total that is 11,564 days, exactly 1,652 weeks or 277,536 hours, and 31.66 years in decimal form. Their next birthday, January 15, 2027, falls on a Friday and is 124 days away, when they turn 32.
Months have different lengths, so the day count needs a clear rule. The calculator adds whole months to the date of birth for as long as the result does not pass the "as of" date, and the days left over are what remains. Someone born on January 31 who is measured on March 1 of a non-leap year has completed no full months yet, because January 31 plus one month would land on February 31, which does not exist and rolls over to March 3. Their age is 0 months and 29 days, which is exactly the gap between the two dates.
A February 29 birthday follows the same logic. In a year without a February 29, the birthday is counted as March 1. A person born on February 29, 2000 is 0 years, 11 months and 30 days old on February 28, 2001, and exactly 1 year old on March 1, 2001. Different places apply different rules to leap-day birthdays, with some using February 28, so for legal purposes such as a driving licence or a contract, check the rule that applies to you.
A year is not always 365 days, so the number of days in a given age depends on the birth date. Someone born June 15, 2007 turned 18 on June 15, 2025 after 6,575 days, because their life included five February 29ths. Someone born June 15, 2005 turned 18 on June 15, 2023 after 6,574 days, having lived through only four. A person born June 15, 2004 reached 21 after 7,670 days, and one born June 15, 1960 reached 65 after 23,741 days. Dividing days by 365 would put all of these off by several days, which is why a calendar-based calculation is more accurate than simple division.
Add a second date of birth to see the difference. Someone born January 15, 1995 and someone born June 30, 1998 are 3 years, 5 months and 15 days apart, which is 1,262 days. The order does not matter. The calculator always measures from the earlier date to the later one. This is useful for comparing siblings, checking the age difference in a couple, or seeing how far apart two classmates are for a school cutoff.
To count the days between any two dates, not just from a birthday, use the date calculator. Planning ahead for a baby? The due date calculator estimates the due date and the baby's gestational age.
How exactly is age calculated here?
The calculator counts every full year between the birth date and the "as of" date, then the full months, then the remaining days. It adds whole months to the birth date until the next month would pass the "as of" date. This avoids the rounding errors you get from dividing total days by 365.
Why is my total days lived not a round number?
Because months have different lengths and every fourth year, apart from some century years, has an extra day. Total days lived is a plain count of every calendar day between the two dates, including any February 29 in the range.
Can I calculate age as of a date other than today?
Yes. Change the "as of" field to any date. Use a past date for a historical age, or a future date to see how old someone will be. The "as of" date cannot be earlier than the date of birth.
Does this account for leap years?
Yes. Day, week and hour totals include every February 29 in the range, and the years, months and days breakdown handles short and long Februaries correctly. A February 29 birthday is counted as March 1 in years that have no February 29.
How do I find someone's age at a specific date in the past?
Enter the birth date, then set the "as of" field to the past date. For example, to see how old someone was on the first day of school, use that day. The tool returns the exact years, months and days on that date.
How is the age gap between two people worked out?
Enter the second birth date in the optional field. The calculator measures from the earlier birth date to the later one and shows the gap in years, months and days, using the same rules as an age. It does not matter which person you enter first.
What if I only know the month and year of birth?
Use the 1st of that month as a stand-in. The years and months will be right, and the day count will be off by at most a few weeks. That is fine for an estimate, but not for anything that needs an exact date, such as legal paperwork.
Can I use this for a pet or a non-human age?
Yes. The maths works for any start date, so you can use it for a pet, a company or a building. It gives the calendar age only. Converting a dog or cat age into "human years" uses different formulas that vary by breed and size.