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Age Calculator

Your exact age in years, months and days — or the gap between any two dates. Leap years and 29 February birthdays are handled properly, and the arithmetic is shown so you can check it.

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  • Nothing leaves your browser

Defaults to today. Change it to work out an age on any date.

Loaded with an example. Type over either field.

Age

36years

36 years old

Months
432
Weeks
1,878
Days
13,149
Hours
315,576

Born on a Wednesday

Turns 37 in 365 days, on 15 August 2027

The working

  1. 15 August 1990 → 15 August 2026
  2. 2026 − 1990 = 36 years, adjusted for the month and day
  3. = 36 years
  4. Total days: 13,149

Check this before you rely on it. A free everyday calculator, provided as a guide — not tax, accounting, financial or legal advice. The working is shown above so you can verify it against your own figures. See our terms of use.

How it works

STEP 1

Enter the date

Your date of birth, or any start date. The second field defaults to today, so an age appears straight away — change it to work out an age on a past or future date.

STEP 2

Read the breakdown

Years, months and days, plus the same span expressed in whole months, weeks, days and hours. Each is counted properly rather than divided by an average month length.

STEP 3

Check the working

The steps are shown underneath, along with the weekday you were born on and a countdown to the next birthday.

What this doesn't cover

Knowing where a calculator stops is what makes the rest of it trustworthy.

  • Times of dayWhole calendar dates only. Someone born at 11pm and someone born at 1am on the same date come out identically, which is how age is counted in everyday and legal use.
  • Time zonesDates are treated as plain calendar dates. If you were born in a different time zone, the date on your birth certificate is the one to enter.
  • Dates before 1582The Gregorian calendar is applied to all dates, including ones before it was adopted. Historical dates that far back will not match contemporary records.
  • Average monthsMonths are real calendar months, not a flat 30 days. That is why the month count here can differ from tools that divide the total days by 30.

Common questions

How is age calculated exactly?

You are a year older on the calendar date of your birthday. The calculator counts whole years first, then whole months, then the leftover days — so 15 August 1990 to 14 August 2026 is 35 years and 11 months, and it becomes 36 years the following day.

What happens if you were born on 29 February?

In a leap year the birthday is 29 February. In a common year the calculator treats 1 March as the anniversary, which matches how age is defined in UK law — someone born on 29 February 2004 turned 18 on 1 March 2022, not 28 February.

Why does 31 January to 1 March show as 1 month and 1 day?

Because a month is complete only once the day-of-month is reached, and there is no 31 February to land on — so the anniversary clamps to 28 February and the remaining day is counted from there. By the same rule, 31 January to 28 February is 28 days rather than a whole month.

Why is the number of months not just the days divided by 30?

Because months are not 30 days. Dividing by 30 drifts by about five days a year and gets steadily more wrong the longer the span. This counts actual calendar months, then measures the leftover days.

Can it work out how many days until a future date?

Yes — use the "Between two dates" tab with today as the start and the future date as the end. It gives the total in days, weeks and months.

Is my date of birth sent anywhere?

No. The whole calculation runs in your browser. Nothing is uploaded, stored or logged.

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