Everyday math
Calculate an age from a date of birth and today.
Enter your numbers to see the answer.
Age calculator guide
The age calculator counts completed years between a date of birth and a chosen date, which by default is a recent day but can be any date in the past or future. It applies the everyday convention: you turn a year older on your birthday, not before, so the result increases by one only when the birthday month and day have arrived in the target year. This is exclusive counting of the current partial year, matching how ages are stated on forms, at borders, and for eligibility rules. The tool works with calendar dates only. Times and time zones play no part, so a birth at 11 p.m. and one at 1 a.m. on the same date give the same age, and the result does not shift when you travel. Leap years are handled by the calendar arithmetic itself; someone born on 29 February is treated as having their birthday on 1 March in years without a 29 February. For the number of days, weeks, or months between two dates rather than whole years, use the date difference calculator.
Age (years) = target year − birth year, minus 1 if the target date falls before the birthday (month and day) in the target year.
Worked example with the defaults: date of birth 20 May 1990, calculated on 19 August 2026. Start with the year difference: 2026 − 1990 = 36. Then check the birthday: 20 May 2026 is before 19 August 2026, so the birthday has already passed and no adjustment is needed. Age = 36 years, which the calculator displays. If the target date were 19 May 2026, one day before the birthday, the result would be 36 − 1 = 35 years. For reference, the two default dates are 13,240 days apart.
Enter both dates using the date picker; internally they follow the ISO 8601 year-month-day form (1990-05-20). The result is whole completed years only, with no months or days remainder. A target date earlier than the date of birth produces a negative or zero figure, which signals swapped fields. Time of day and time zone are not used.
The result follows directly from the numbers you entered, so its accuracy is the accuracy of those inputs. The most common source of a surprising answer is a mismatch between the question you meant to ask and the one the calculator answered, so re-read the field labels if the figure looks wrong. The formula is shown above so you can check the arithmetic yourself. On this page the figure rests entirely on date of birth and calculate age on, so start there if the age calculator returns something you did not expect.
Good to know: age is not simply the difference between years. Someone born in December 1990 is 35, not 36, for most of 2026. Inclusive counting (treating the birth day itself as day one, as in some East Asian age systems) gives a number one higher than this calculator. The “calculate age on” field defaults to a fixed recent date rather than live today, so update it for the current day. A 29 February birthday advances on 1 March in common years.
Results are planning estimates. Check the units, product coverage, carrier rules, or local rates before making a purchase or financial decision.
Sources
How it works
Calculate an age from a date of birth and today. This tool explains the calculation so you can adjust the assumptions to match your situation.
Worked example
With Date of birth = 1990-05-20 · Calculate age on = 2026-08-19 → 36 years (age on the selected date). Change an input above and this example updates with your numbers.
Common questions
On 19 August 2026 they are 36 years old: 2026 − 1990 = 36, and the May birthday has already passed. On any date from 20 May 2026 to 19 May 2027 the answer stays 36.
Subtract the birth year from the current year, then subtract one more if this year’s birthday has not happened yet. Born 20 May 1990 and checking on 19 May 2026 gives 2026 − 1990 − 1 = 35.
A person born on 29 February has a birthday only every four years on the calendar, but their age still increases annually. In years without a 29 February this calculator counts the new age from 1 March, the first day after 28 February.
No. The calculator compares calendar dates only, so the hour of birth and the time zone where you are now are ignored. Your age changes at the start of your birthday in whatever calendar you are reading.
Exclusive counting, used here and on official documents in most countries, counts completed years: a newborn is 0. Inclusive systems count the birth year as year one, so the same person is one year older. Over 36 completed years the inclusive figure would be 37.