Age Calculator
Exact age in years, months, days, and more.
The Age Calculator tells you exactly how old you are in years, months, and days, plus total days, weeks, and hours lived — and how many days until your next birthday.
How Age Is Calculated Exactly
Years, months, and days — exact calculation
Age is calculated by subtracting the birth date from a target date in three steps: first count full years, then remaining full months, then leftover days. Each step borrows from the previous unit when the subtraction would go negative — for example, if the birth day is the 28th and the target day is the 5th, one month is borrowed and the day difference is recalculated. This gives an exact result rather than an approximation from dividing milliseconds.
Leap years and month lengths
February has 28 days in regular years and 29 in leap years (divisible by 4, except centuries not divisible by 400). This means a simple division of days-elapsed by 365.25 gives a fractional approximation, not a true age. The calculator handles both automatically. People born on February 29 have their birthday counted on February 28 in non-leap years — which is the standard legal and medical convention in most countries.
Age = Target date − Birth date (exact years, months, days)Total days = (Target − Birth) ÷ 86,400,000 msTotal hours = Total days × 24 When exact age matters
Age verification is the most common use case: alcohol purchase age, driving license eligibility, pension and retirement qualification, voting rights, and medical screening thresholds (e.g., cancer screening starting at 45 or 50 years). Legal documents like wills, insurance policies, and court records often require age stated in years and days. The optional second date field lets you calculate your age on any past or future date — useful for checking retirement eligibility on a planned exit date, or for historical records.
Total days lived — a different perspective
Seeing your total days lived puts time in a different frame. A 30-year-old has lived roughly 10,950 days. A 65-year-old has passed 23,725 days. Total hours lived is often an even more striking number — at 40 years old, you have lived approximately 350,400 hours. Many people use this figure in productivity and life-planning contexts to visualize how time actually distributes across sleep, work, and free time.
Frequently Asked Questions
How do I calculate my exact age in days?
Subtract your birth date from today's date to get the total number of days. The calculator does this automatically and shows total days in one of the result cards.
What happens if I was born on February 29?
In non-leap years, your birthday is counted on February 28. The calculator handles this automatically so your age is always correct.
Can I calculate how old I will be on a future date?
Yes. Enter your date of birth, then enter any future date in the optional second field. The calculator will show your exact age on that date.
How many days until my next birthday?
The last result card shows the number of days until your next birthday based on today's date. If today is your birthday, it shows 'Today!' and counts to next year.
Is this calculator accurate for very old or very young ages?
Yes. The calculator uses JavaScript Date objects that handle centuries of dates correctly. It works for any birth date from historical records to recent births.
What is the formula for the Age Calculator?
Age = Target date − Birth date, broken into full years, then remaining months, then remaining days. Total days = (Target date − Birth date) in milliseconds divided by 86,400,000. Weeks = total days divided by 7. Hours = total days multiplied by 24.