Age Calculator
Exact age in years, months, weeks and days from a date of birth — plus the total in months, weeks, days, hours, minutes and seconds, and your next birthday.
🔒 Calculated in your browser — no dates are uploaded.
Work out an exact age
Enter a date of birth (and optionally a reference date, which defaults to today) to see the exact age in years, months, weeks and days. Yesterday, Today and Tomorrow are one click each, so "how old will I be tomorrow" needs no date picking. Useful for birthdays, forms, eligibility and milestones. All the date maths runs in your browser.
The same age, said the way the form wants it
Under the headline the same span is rolled up two other ways — as whole months with the days left over, and as whole weeks with the days left over — and then counted in months, weeks, days, hours, minutes and seconds side by side. Narrow that row to a single unit with Show resulting age in when only one number is wanted. Below it sit the day of the week you were born on and your next birthday, written as a date in your own language with the weekday it falls on, plus the countdown to it. Copy the whole answer as text, or copy the link — both dates travel in the URL, except an as-of date of today, which is left out so the link counts to the day it is opened — and Reset puts the form back.
How it is calculated
The age is built from calendar months and days — anchoring the date of birth forward and clamping to the length of the target month — so it matches how people actually count age, and it accounts for different month lengths and leap years. Total days are counted in UTC, so a daylight-saving change in the span cannot add or drop a day.
Frequently asked questions
Can I calculate age on a past or future date?
Yes. Change the "As of" date to any reference date and the age is computed for that day, or use the Yesterday / Today / Tomorrow buttons beside it.
Does it handle leap years?
Yes. The calculation uses real calendar dates, so leap days and varying month lengths are accounted for.
What happens with a 29 February birthday?
In a year that has no 29 February the anniversary is taken as 28 February — the last day of that month — and both numbers on the page agree about it: the years/months/days breakdown and the countdown to the next birthday use the same rule, so you are never told it is your birthday and that it is still a day away. The year after the clamp is the leap year itself, so the next birthday shown is 29 February again.
Can I get the age in one unit, like months or seconds?
Yes. Every unit is shown at once by default — months, weeks, days, hours, minutes and seconds — and the "Show resulting age in" menu narrows the row to just the one you need. The two "or …" lines above it give the mixed forms a form usually asks for: whole months plus days, and whole weeks plus days.
Are my dates uploaded?
No. Everything is calculated locally in your browser.