Age Calculator
Free age calculator. Find your exact age in years, months, and days, days lived, and days until your next birthday. No signup.
What is an age calculator?
An age calculator computes an exact age in years, months, and days between a date of birth and any target date. It’s the precise version of “how old am I?” — useful for eligibility windows, planning, and records.
How this calculator works
- Enter a date of birth and an optional “as of” date (blank uses today).
- It subtracts year, month, and day fields with borrow rules so months are calendar-accurate.
- Total days lived and days until the next birthday round out the picture.
- Age is counted in complete calendar units — partial months don’t count until the date passes.
How to use the result
- Use the “as of” date for legal or medical eligibility on a specific day — not just today.
- Read the age as complete years, months, and days — two people can both be “36” while differing by weeks.
- Use days-to-birthday for countdowns, or months for planning milestones.
- For legal purposes, confirm which date convention your jurisdiction uses — some count from the day after birth.
How is age calculated?
Start from the birth year and subtract, then adjust for month and day with borrowing from the higher units when needed. Someone born May 15, 1990, on August 12, 2026 is 36 years, 2 months, and 28 days old — the full units after 36 years of May 15 milestones.
Common mistakes
- Rounding to whole years. “Almost 37” and “just turned 36” are a year apart in common speech but can be days apart in real life.
- Off-by-one on birthday days. Whether you’re a full day old on the birthday depends on time-of-day conventions.
- Using calendar days for months. Months are calendar units — a month is not always 30 or 31 days.
Age math is date math, and it pairs naturally with the due date calculator’s week-by-week gestation tracking and the retirement calculator’s age-to-age projection. For simple arithmetic checks, the basic calculator is always there.