Age Calculator
Your age is more than a number on a birth certificate — it's the exact span of years, months and days since you were born, and knowing it precisely matters for official forms, age limits and milestone planning. Enter your date of birth and this calculator instantly works out your calendar age, broken down into years, months and days, plus the total number of days you've lived. Leap years and whether your birthday has already happened this year are accounted for automatically, so the result is always exact.
結果
フィールドに入力して結果を確認してください。
公式
Age = today − date of birth, split into years, months and days
The calculator first subtracts the birth year from the current year for a provisional number of years. If your birthday hasn't happened yet this year, one year is subtracted and twelve months borrowed; the same borrowing happens at the day level if today's date falls earlier in the month than your birth date. This is exactly how you'd count age by hand on a calendar, which is why the result always matches official age calculations. The total day count is calculated separately, as the full number of calendar days between the two dates.
ステップ解説
- 1Enter your date of birth in the date field.
- 2The calculator compares it with today's date.
- 3Read off your age in years, months and days, plus the total number of days lived.
計算例
Born 15 May 1990
→ On 24 July 2026: 36 years, 2 months, 9 days.
Born on leap day, 29 February 2000
→ On 6 August 2026: 26 years, 5 months, 8 days (9,655 days in total).
Born 31 December 1995
→ On 1 January 2026: 30 years, 0 months, 1 day — the birthday was just the day before.
Reference table
| Age (years) | Approx. days | Approx. weeks |
|---|---|---|
| 1 | 365 | 52 |
| 10 | 3,653 | 522 |
| 18 | 6,575 | 939 |
| 21 | 7,670 | 1,096 |
| 30 | 10,958 | 1,565 |
| 50 | 18,263 | 2,609 |
| 65 | 23,741 | 3,392 |
| 100 | 36,525 | 5,218 |
Based on an average year of 365.25 days (accounting for leap years); your exact age in days depends on how many leap years you've lived through.
よくある間違い
- Simply subtracting the birth year from the current year without accounting for whether the birthday has passed yet.
- Estimating age in days by multiplying years by 365 and forgetting leap years.
- Assuming age in 'complete years' equals the raw calendar-year difference, when that's only true once this year's birthday has passed.
活用シーン
- Checking your exact age for an official form.
- Determining eligibility for an age-restricted service, such as voting, driving or pension.
- Working out a child's exact age in months for medical check-ups or developmental milestones.
よくある質問
Does this also work for future dates?
No, this calculator computes age up to today; for a future date, use the countdown calculator.
How is a birthday on 29 February handled?
In years without a 29 February, the comparison is automatically corrected as the month count continues, so you don't lose or gain a day over multiple years.
Why doesn't my age in days exactly equal years × 365?
Because leap years add an extra day roughly every four years, so the exact day count is always slightly higher than years × 365.
Does the calculator account for time zones?
No, it uses your device's local calendar date, not UTC, so the result matches the date on your own calendar regardless of time zone.
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