Age Calculator

How the Age Calculator Works

Enter your date of birth and the calculator compares it against today’s date. If you want your age on a different date, perhaps for a form, an application or simple curiosity, change the second date and the tool recalculates instantly.

The result appears in chronological order, full years first, then remaining months, then remaining days. Below that you will find your age broken down into single units, so you can finally answer questions like how many days old am I or how many weeks have I been alive.

How Age Is Calculated

Working out age by hand means subtracting one date from another and that is trickier than it looks. Months contain 28, 29, 30 or 31 days and leap years add an extra day every four years with exceptions for most century years. Get either wrong and your answer drifts.

The manual method sets the dates up like long subtraction. Subtract the days first, borrowing from month where needed. Then subtract months, borrowing from the year if required. Finally subtract the years. Someone born on 15 March 1990 checking their age on 11 July 2026 would get 36 years, 3 months and 26 days.

The calculator handles every leap year and month length automatically, which is why it stays accurate where mental arithmetic and rough formulas slip.

Chronological Age vs Biological Age

Your chronological age is time elapsed since birth. It never varies and it is figure every official document uses. Biological age is different. It describes how old your body appears based on factors like genetics, lifestyle, fitness and health conditions. Two people with same chronological age can have very different biological ages, which is why the two terms should never be mixed up on medical or insurance paperwork. This calculator measures chronological age only.

Age Milestones That Matter in the UK

Knowing your exact age matters most when it decides what you can do. These are the key UK milestones:

• At 16 you can leave school in some circumstances, work more hours and ride a moped
• At 17 you can hold a provisional licence and drive a car with supervision
• At 18 you can vote in general elections, buy alcohol and sign contracts
• School entry works on a 1 September cut off in England and Wales, so a child born on 31 August starts a full year before one born a day later
• State Pension age is currently rising from 66 to 67 for those born after April 1960, with the change phasing in between 2026 and 2028

For pension planning the exact date matters, so use the calculator to check your age on the date you expect to retire rather than relying on years alone.

Working Out a Baby’s Age in Weeks and Months

Parents of newborns count age differently. Health visitors, vaccination schedules and developmental checks all run on weeks for the first few months and then months up to age of two. Enter your baby’s date of birth and the calculator shows their age in weeks and months automatically, which saves counting through the calendar every time a form asks.

One thing worth knowing: a month of age is calendar based, not a fixed 4 weeks. A baby who is 12 weeks old is not quite 3 calendar months old. The calculator keeps both figures accurate so you can give whichever one the paperwork wants.