Question 1

How do I calculate my exact age?

Accepted Answer

Enter your date of birth and the calculator subtracts it from today's date, returning the result as completed years, months, and days. Months are counted on the calendar — from your birthday in one month to the same date in the next month — so a Y/M/D result like 28 years, 4 months, 11 days lines up exactly with how birthdays are normally counted.

Question 2

How many days old am I?

Accepted Answer

Your age in days is the count of midnights between your date of birth and today. The calculator shows this directly in the Total days card. As a rough check, multiply your age in years by 365.25 — for someone aged 30 that is about 10,958 days.

Question 3

What is chronological age?

Accepted Answer

Chronological age is the time that has elapsed between your date of birth and a given date, usually today. It is what this calculator returns. It is distinct from biological or developmental age, which try to estimate how the body is functioning relative to its years.

Question 4

How is age calculated across leap years?

Accepted Answer

The calculator works in real calendar dates, so leap days are counted automatically. Your age in completed years only ticks up once your birthday passes in the current year, and the Total days figure includes every February 29 you have lived through.

Question 5

How do I calculate someone's age from their date of birth?

Accepted Answer

Subtract their date of birth from the target date. If the target date's month and day are before their birthday in that year, subtract one from the year difference. The calculator handles this for you — enter their date of birth and switch to Tab B if you need their age on a date other than today.

Question 6

What is my age in months?

Accepted Answer

Total months is the number of completed calendar months between your date of birth and today. The calculator shows this in the Total months card. For someone aged 28 years and 4 months, the total is 340 months.

Question 7

How old am I in weeks?

Accepted Answer

Your age in weeks is your total days divided by seven, rounded down. The calculator shows this in the Total weeks card. Someone who is 10,000 days old is roughly 1,428 weeks old.

Question 8

How do I find out what day I was born on?

Accepted Answer

Enter your date of birth and the Next birthday section reports the weekday of your upcoming birthday. To find the weekday of your birth, set Tab B's target date to your date of birth — the day of the week appears in the result line.

Question 9

Can I use this to calculate a child's age?

Accepted Answer

Yes. Enter the child's date of birth as you would your own. For very young children the Total days and Total months figures are often more useful than years. Newborn and infant growth tracking has dedicated tools under Health & Body.

Question 10

What is the difference between age in completed years and age in decimal years?

Accepted Answer

Completed years is how old you are today — it only increases on your birthday. Decimal years expresses the same age as a single number, including the fraction of the year since your last birthday. Someone whose last birthday was 4 months and 11 days ago is 28 completed years old but about 28.37 in decimal years.

Age Calculator — Exact Years, Months, Days & Hours

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