Most of the time we only need our age in whole years. But forms, school admissions, sports categories and insurance quotes sometimes ask for an exact age, or your age on a specific date. Here is how to work it out without getting tangled in calendar quirks.
The step-by-step method
- Write the later date (usually today) and the date of birth as year, month and day.
- Subtract the days. If the answer is negative, borrow the number of days in the previous month and reduce the month count by one.
- Subtract the months. If the answer is negative, borrow 12 months and reduce the year count by one.
- Subtract the years.
A worked example
Born on 15 March 1995, checking on 3 November 2026. Days: 3 − 15 is negative, so we borrow the 31 days of October: 34 − 15 = 19 days, and the month count drops from 11 to 10. Months: 10 − 3 = 7 months. Years: 2026 − 1995 = 31 years. The answer is 31 years, 7 months and 19 days.
How leap years affect age
A person born on 29 February only has a calendar birthday every four years. In other years, countries and organisations use either 28 February or 1 March as the legal birthday. If an exact day matters, such as for a driving licence or a legal age, check which rule applies where you live.
Different ways of counting age
The international system counts completed years from birth, which is what most calculators use. Traditional East Asian age reckoning counted a person as one year old at birth and added a year at each new year. South Korea moved to the international system for most legal and administrative purposes in 2023, although you may still meet the older style in conversation.
Why people want exact age
- Entry cut-off dates for schools and youth sports.
- Eligibility rules for jobs, benefits and insurance.
- Pregnancy, baby and toddler milestones counted in months or weeks.
- Fun facts, such as how many days old you are.
To skip the arithmetic, use our free Age Calculator. For the gap between any two dates, try the Days Between Dates Calculator.
Frequently asked questions
How many days old am I?
Multiply your age in years by 365, then add one day for each leap year you have lived through. A calculator is much quicker and exact.
Is age counted from the day of birth or the day after?
You turn a year older on the anniversary of your birth date.
This guide is for general information only. See our disclaimer.