Birthday age calculator

Exact age in years, months and days, how long until the next birthday, the day of the week they were born, and the number of candles the cake needs. Runs in your browser; nothing is stored.

What it tells you

  • Exact age in years, months and days, counted the way people say it out loud, not as a decimal.
  • Next birthday: the date, the weekday it falls on, how many days away it is, and the age they are turning. That last number is the one you need for the candles.
  • Day of the week they were born, which almost nobody knows about themselves and everybody wants to.
  • Days, weeks and hours lived, counted through every leap year in between.
  • Star sign, for the card, the cake topper, or the argument.

Why the “as of” date is there

It defaults to today, which answers “how old are they right now.” Change it to answer other questions: how old will they be on the wedding date, how old was Grandma when she moved countries, exactly how old is the baby on the day of the christening. Set it to the next birthday and the result is a round number.

To compare two people instead, the age difference calculator gives the exact gap between two birth dates, and the part of each year when they are a year further apart.

From the number to the card

The interactive birthday card on this site shows a 3D cake the recipient blows out using their phone, and then their age on the cake above your message. Enter a date above, and the button under the result opens the card creator with the age and name already filled in. If the birthday is a big round one, the milestone birthday wishes guide has lines for it.

Common questions

How is the age in years, months and days worked out?

Whole years first, then whole months, then the days left over, the same way people count it out loud. Someone born on 31 January is one month old on 28 February (or 29 February in a leap year), because that is the last day of the following month.

What about a 29 February birthday?

In years without a 29 February the next birthday is counted on 28 February, which is the convention most countries use for legal ages. If your family celebrates on 1 March instead, add one to the days-until figure.

Why is the total number of days not simply the age times 365?

Leap years. Every fourth year (with a couple of exceptions) has 366 days, so a 40-year-old has lived roughly ten more days than 40 times 365. The calculator counts actual calendar days between the two dates.

Is anything I enter saved?

No. The calculation runs entirely in your browser. Nothing is sent to a server and nothing is stored.