Age Calculator

Chronological age is calendar days between birth date and target date, broken into completed years, months and days. The tricky part is calendar drift — months have 28 to 31 days, and every 4 years February has 29. Our calculator counts complete years first (the birthday test: if this year's birthday hasn't happened, subtract one year), then complete months from the last birthday, then remaining days from the last monthly anniversary. Total days come straight from the calendar difference, accounting for every leap day between birth and today. Total hours, minutes and seconds are derived from the day count × 24, ×1440, ×86400 respectively.

Years and months matter for most legal and social purposes, but some contexts want precision: pediatricians track infant age in weeks or months, geneticists track generation time in years and months, and people celebrate milestone 'day ages' like 10,000 days (≈27.4 years) or 1 billion seconds (≈31.7 years). Our calculator shows your age across all useful granularities at once. A 30-year-old has lived roughly 10,958 days, 1,566 weeks, 262,968 hours, 15,778,080 minutes and 946,684,800 seconds. Leap days add up: someone born in 1990 has experienced 9 leap days by 2026.

The age-gap math is a simple date subtraction, but interpretation depends on context. For couples, the 'half your age plus seven' heuristic (a 40-year-old's minimum partner age is 27) is folklore, not law — legal adulthood governs. For siblings, a gap under 2 years can mean overlapping developmental stages; over 6 years often means near-independent upbringings. Enter two birth dates to see the exact gap in years, months and days. Note: this calculator computes chronological difference only, not cohort or generation difference (see Generations section).

Planning for milestones? Enter a future date and see your exact age on that day. Common uses: when will I reach retirement age (65 or 67 depending on country)? When is my child eligible for kindergarten (usually age 5 by September 1 in the US, 4-5 depending on UK cutoff rules)? When can I take early Social Security (age 62 in US) vs full benefits (age 67 for 1960+ births)? When does my teen legally become an adult (age of majority)? Use this alongside the Date Calculator to plan your calendar around age thresholds.

Age of majority is when you become legally an adult — able to sign contracts, vote, serve in the military and be tried as an adult. United States: 18 in all states except Alabama and Nebraska (19) and Mississippi (21). United Kingdom: 18 across England, Wales, Scotland and Northern Ireland. Canada: 18 in Alberta, Manitoba, Ontario, Quebec, Saskatchewan and PEI; 19 in BC, New Brunswick, Newfoundland, Nova Scotia, NWT, Nunavut and Yukon. Australia: 18 nationwide. Age of majority differs from other age thresholds (voting, drinking, driving) which have their own rules — see the next section.

These are the thresholds most people actually care about, and they differ widely within and between countries. Voting: US federal 18 (some states 17 for primaries); UK 18 (Scottish parliament 16); Canada 18 federal; Australia 18 (enrolment compulsory). Drinking (legal alcohol purchase): US 21 nationwide; UK 18; Canada 18 in Alberta/Manitoba/Quebec, 19 elsewhere; Australia 18. Driving (full license age varies by class; below is typical for a car): US 16-17 depending on state, with graduated licensing; UK 17 (provisional from age 15 years 9 months); Canada 16 typical (learner from 14 in Alberta); Australia 17-18 depending on state. Always verify with local licensing authorities.

Retirement ages have been rising globally. United States: Social Security full retirement age (FRA) is 66 for those born 1943-1954, graduating to 67 for anyone born 1960 or later. Reduced benefits available from 62; delayed retirement credits up to age 70. United Kingdom: State Pension age is 66 in 2026, rising to 67 between 2026-2028 and 68 phased 2044-2046. You can defer for higher weekly payments. Canada: CPP/QPP standard retirement age is 65; reduced if taken 60-64, enhanced if deferred 65-70. OAS begins at 65. Australia: Age Pension qualifying age is 67 for anyone born on or after 1 July 1957. Super (superannuation) preservation age is 60. All four systems reward delayed claims and penalize early ones; model before deciding.

About 1 in 1,461 people is born on February 29 — a leap day that only occurs every 4 years (with the century-year exception: 1900 wasn't leap, 2000 was, 2100 won't be). 'Leapers' or 'leaplings' have several options for celebrating in non-leap years. Legally, most jurisdictions treat February 28 as the birthday for age-of-majority purposes (you turn 18 on Feb 28 in a non-leap year, not March 1). Australia and UK: Feb 28 for legal purposes. US varies by state. Our calculator correctly counts all leap days between birth date and target date — someone born Feb 29, 2000 has 'had' 7 actual birthdays by 2028 but is chronologically 28 years old.

Chronological age is your calendar age — what this calculator measures. Biological age is how old your body actually is, estimated from health markers: telomere length, epigenetic clocks (DNA methylation), VO₂ max, arterial stiffness, metabolic panels. A 50-year-old can have a biological age of 40 (lifestyle-fit) or 60 (chronic disease). Biological age tests are commercially available (e.g., GlycanAge, TruAge) and gaining medical acceptance. This calculator gives chronological age only — use it for legal documents, age thresholds and social contexts. Use biological age testing if you want the 'how old are you really' answer for health purposes.

The folk rule '1 dog year = 7 human years' is wildly oversimplified. Current veterinary science for dogs: year 1 ≈ 15 human years, year 2 ≈ 24, then +4 to +5 per year depending on breed size. A 2019 UC San Diego study proposed an epigenetic formula: human_age ≈ 16 × ln(dog_age) + 31. Under this, a 5-year-old dog is biologically ~57 in human terms; a 12-year-old dog is ~71. Large breeds age faster than small — a 10-year-old Great Dane is ~85, a 10-year-old Chihuahua ~56. Cats: year 1 ≈ 15 human, year 2 ≈ 24, then +4 per year. A 15-year-old cat is ~76 in human terms. Our calculator outputs chronological pet age in years and days; multiply by the appropriate breed-size factor for a human-equivalent estimate.

Using (current_year − birth_year) as age. Wrong for anyone whose birthday hasn't happened this year. Born July 5, 1990; today is March 15, 2026 — you're 35, not 36. Ignoring leap years in day-count age. 30 × 365 is 10,950 days; actual day-count for 30 years is typically 10,957-10,958 depending on birth date (includes 7-8 leap days). Confusing age-in-months with age in completed months. A baby who is 18 months 20 days old is '1 year and 6 months' in age, not '1 year, 8 months' (that's 18 months + 20 days misread as 20 months). Assuming international age-of-majority is 18. Most are 18, but Alabama, Nebraska, Mississippi and several Canadian provinces are not. Forgetting Korean/Chinese traditional age. Still used informally in some contexts — adds 1-2 years to Western age. Pet age × 7. See prior section — use the logarithmic formula for dogs, linear for cats.