Age Calculator

An age calculator works out exactly how old someone is in years, months and days, without counting on your fingers or tripping over short months and leap years. Enter a date of birth and our free tool shows the exact age today or on any date you choose, plus the total months, weeks, days, hours and minutes, the day of the week you were born and a countdown to the next birthday. A second mode measures the time between any two dates. People born on 29 February are handled properly too, with a clear explanation of how UK law treats leap-day birthdays and the option to use 1 March or 28 February. Everything is calculated in your browser.

How to use the Age calculator

1. 1 Enter the date of birthUse the date picker or type the date. The result appears as soon as the date is complete.
2. 2 Choose the date to measure toIt is today by default. Change it to find someone's age on a past or future date, such as the start of a school year or a policy date.
3. 3 Read the exact ageThe headline shows years, months and days. Below it are the day of the week of birth, the next birthday countdown and the totals.
4. 4 Set the leap-day rule if neededFor someone born on 29 February, choose whether birthdays in non-leap years fall on 1 March or 28 February.
5. 5 Switch to date difference for anything elseUse "Difference between dates" to measure the time between any two dates, optionally including the end date.

How exact age is calculated

Counting age in whole years is easy: you are one year older on each birthday. Years, months and days are trickier, because months have between 28 and 31 days. The calculator counts complete years first, then complete months since the last birthday, then the remaining days. A complete month runs from a given day in one month to the same day in the next. So from 15 March to 14 April is 30 days, but from 15 March to 15 April is exactly one month.

When the starting day does not exist in a shorter month, the calculator uses the last day of that month. One month after 31 January is 28 February, or 29 February in a leap year, and one month after 31 March is 30 April. This is the same approach used by most date libraries and spreadsheet functions, though a few tools handle the end of the month differently, so you may occasionally see a one-day difference in the days figure from another calculator.

The totals are simpler. Total days is the exact number of calendar days between the two dates. Total weeks divides that by seven and shows any days left over. Hours and minutes multiply the days by 24 and 1,440, measured from midnight to midnight. They ignore the time of day you were born and the hour gained or lost when the clocks change, so treat them as a fun approximation rather than an exact count.

Leap years and 29 February birthdays

A leap year has 366 days, with an extra day on 29 February. Under the Gregorian calendar used in the UK, a year is a leap year if it divides by 4, except for century years, which must divide by 400. So 2024 and 2028 are leap years, 2100 will not be, and 2000 was. The calculator applies these rules automatically, which matters when you count days across many years.

Someone born on 29 February only has a true birthday every four years, so the question is when they become a year older in between. In Scotland the law answers it directly. Section 6 of the Age of Legal Capacity (Scotland) Act 1991 says that a person born on 29 February in a leap year has their relevant anniversary on 1 March in a year that is not a leap year. In England and Wales, the Family Law Reform Act 1969 says a person reaches an age at the start of the relevant anniversary of their birth, but it does not say which day that is for a leap-day birthday. 1 March is the common reading, but some organisations use 28 February.

Because of that uncertainty, the calculator lets you choose. The default is 1 March, which follows the Scottish rule and the usual interpretation elsewhere. Switch to 28 February if that is what a particular organisation uses. When the date of birth is 29 February, a table shows the next few non-leap-year birthdays under both rules. If a legal age matters, such as for a driving licence, a pension or a contract, confirm the rule with the organisation concerned.

Measuring the time between any two dates

The date difference mode works exactly like the age calculation, but for any pair of dates. Use it to see how long you have been in business, how long ago a policy started, how many days remain until a wedding or a lease break, or the length of a project. If you enter the dates in reverse order, the tool swaps them and tells you.

By default the end date is not counted, so from Monday to Tuesday is one day. Tick "Include the end date" when you need to count both days, for example to find how many days a hotel stay, an event or a period of leave covers on the calendar. That adds one day to the total and can change the months and days figure too.

If you need business days rather than calendar days, use our Working Days Calculator, which leaves out weekends and UK bank holidays for England and Wales, Scotland and Northern Ireland.

Common reasons to check an exact age

Most people use an age calculator out of curiosity, but there are plenty of practical reasons to know an exact age or the time between dates.

• School years: in England and Wales, the school year group is set by age on 31 August, and in Scotland the cut-off for starting school works differently, so check the rule for your area.
• Milestones: working out the date of an 18th, 21st, 40th or 100th birthday, or a 10,000th day alive, which is a little over 27 years.
• Business and HR: checking the age of a job applicant where a minimum age applies, or how long an employee has worked for you on a given date.
• Insurance and pensions: confirming the age on a policy date, or how far away a pension age is. Always check the official State Pension age for your date of birth on GOV.UK.
• Family history: finding the age of an ancestor at a census, marriage or death from the dates on a record.
• Pets and possessions: tracking the age of a dog, a car or a piece of equipment from its purchase or registration date.

The day of the week you were born

The calculator shows the day of the week of the date of birth, worked out from the Gregorian calendar. It is accurate for any date since the UK adopted that calendar in September 1752, which covers anyone alive today and most family history research. Dates earlier than that in British records used the older Julian calendar, so the weekday shown for them may not match the original documents.

It also shows the weekday of the next birthday, which is handy for planning a party or booking a table. Birthdays move forward by one weekday each year, or two after 29 February, so a birthday that falls on a Saturday one year will usually be on a Sunday the next.

Privacy and accuracy

Dates of birth are personal data, so the calculator never sends them anywhere. All the arithmetic happens in your browser and nothing is saved, logged or uploaded. You can safely check the ages of staff, customers or family members without the information leaving your device.

The results use calendar dates only and treat every day as starting at midnight. That gives the answer most people expect, but it does mean someone born late in the evening is shown as a day older for most of their birth date than they strictly are. For official purposes, the age an organisation recognises is the one that counts, so use the result as a guide and check their rules when it matters.

Examples you can copy

Date of birth     31 January 1990 (a Wednesday)
Age on            23 October 2026
Exact age         36 years, 8 months, 23 days
Total days        13,414
Next birthday     Sunday 31 January 2027 (turning 37)

Born              29 February 2000
1 March rule      turns 25 on Saturday 1 March 2025
28 February rule  turns 25 on Friday 28 February 2025
Scotland          1 March (Age of Legal Capacity (Scotland) Act 1991, s6)

Common mistakes to avoid

Frequently asked questions