Age Calculator
Enter a date of birth to get the exact age in years, months and days — plus total months, total days, and when the next birthday falls. You can also set a different "as of" date to compute an age on any day, past or future.
How exact age is calculated
Age in years is the number of full birthdays that have passed: you stay 35 until the very day you turn 36. The months-and-days part continues from the last birthday: full calendar months first, then leftover days, borrowing real month lengths (28–31 days) where needed.
This calendar-walking method matches how ages are used legally and medically (chronological age). Total days is the plain day count since birth; dividing it by 365.25 gives an approximate decimal age, but the year/month/day breakdown is the precise form.
Worked examples
Example 1: exact age today
Born May 15, 1990 — how old on November 7, 2026?
- The last birthday was May 15, 2026 — count the full years.1990 → 2026 = 36 years
- Full months from May 15 to November 7: May→Oct is 5 (Nov 15 hasn't come).+ 5 months (to October 15)
- Days from October 15 to November 7.16 (left in Oct) + 7 = 23 days
36 years, 5 months, 23 days old.
Example 2: the day before a birthday
Born November 8, 1990 — how old on November 7, 2026?
- The 2026 birthday hasn't happened yet, so the last one was in 2025.1990 → 2025 = 35 years
- From November 8, 2025 the calendar gives 11 full months and then the days.+ 11 months + 30 days
35 years, 11 months, 30 days — one day short of 36.
Example 3: age in total days
How many days has a person born May 15, 1990 lived by November 7, 2026?
- Count full years in days: 36 years include 9 leap days (1992–2024).36 × 365 + 9 = 13,149 days to May 15, 2026
- Add the days from May 15 to November 7, 2026.13,149 + 176 = 13,325 days
13,325 days (about 1,903 weeks).
FAQ
How does the calculator handle a February 29 birthday?+
In leap years the birthday is February 29 as usual. In common years this calculator uses the February 28 convention for the "next birthday" date; legally, some jurisdictions use March 1 instead — both conventions differ by one day.
Why does my age in months look different from months ÷ 12?+
Total months counts full calendar months from your birth date, so 36 years 5 months = 437 months. It's exact, while dividing total days by 30.44 only approximates.
What is chronological age?+
The time actually elapsed since birth — what this calculator computes. It's the standard for school enrollment and medicine, as opposed to developmental or biological age measures.
Can I calculate age at a date in the past or future?+
Yes — set the second field to any date. That's useful for forms that need your age on a cutoff date (school entry, visas, insurance) rather than today.
In some countries ages are counted differently — which system is this?+
The international (Western) system: you're 0 at birth and gain a year each birthday. Systems like traditional Korean age counting start at 1 and add a year at New Year, so they can differ by up to two years.
Related calculators
- Chronological Age CalculatorCalculate chronological age in years, months and days between birth date and test date — the exact calendar method used in assessments and pediatrics.
- Date CalculatorCount the days between two dates (with weeks and a years/months/days breakdown) or add and subtract days from a date — with the counting logic shown.
- Dog Age CalculatorConvert dog years to human years with the veterinary size chart and the UCSD epigenetic formula — not the old times-7 myth. Steps included.