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概要

年齢計算機

生年月日から正確な年齢を年・月・日で計算。生きてきた日数・週数・次の誕生日までのカウントダウンも表示します。

とはの使い方使用例主な使用シーンよくある質問

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悩み

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#age-calculator#date-of-birth#birthday-calculator#days-lived#next-birthday

Age Calculator

Calculate your exact age in years, months, and days. See days lived, next birthday, and more.

Select your date of birth above

解決できる問題

I need my exact age in years, months, and days for a visa application — how do I find it?

Enter your date of birth into the calculator. The top result shows your age broken down into years, months, and days as of today — the format most visa forms require. The numbers account for varying month lengths and leap years accurately.

How many days until my next birthday?

Enter your date of birth and scroll to the birthday card at the bottom of the result. It shows the exact date of your next birthday and the number of days remaining. If today is your birthday, it displays a celebration message instead.

How many days have I been alive?

Enter your date of birth. The stats section shows your total days lived as an exact integer. For example, someone born on January 1, 1990 has lived over 13,200 days as of 2026. The count also shows weeks and hours for perspective.

How do I check if my child meets the age cutoff for school enrollment?

Enter your child's date of birth. The calculator shows their exact age in years, months, and days as of today. Compare this to your school district's cutoff date and minimum age requirement — typically 5 years old by a specific date in the fall.

How do I find my age in weeks or months instead of years?

The stats cards below the main age display show your total age in months, weeks, and days as single numbers. For example, 30 years is approximately 1,565 weeks or 360 months. These figures are calculated using your exact birth date, not rounded estimates.

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とは

年齢計算機 とは？

The Age Calculator computes your exact age from your date of birth down to the day. Unlike simple year subtraction, it accounts for month and day boundaries correctly — so if your birthday hasn't occurred yet this year, it gives you the right count without rounding errors.

Beyond the core years/months/days breakdown, the calculator shows the total number of days, weeks, months, and hours you have been alive — figures that put life's scale in perspective. It also shows how many days remain until your next birthday, turning an ordinary calculation into a moment worth noticing.

の使い方

年齢計算機 の使い方

1. Click the date input and select your date of birth from the calendar, or type it in YYYY-MM-DD format.

2. Your age in years, months, and days appears immediately.

3. Scroll down to see total days lived, weeks, months, and hours.

4. The birthday card shows days until your next birthday, or celebrates if today is the day.

5. Use the quick-fill buttons (18, 25, 30 years ago) to try example dates fast.

使用例

使用例

Date of birth: 1995-06-15  (today: 2026-04-27)

Age:          30 years, 10 months, 12 days
Days lived:   11,274
Weeks lived:  1,610
Months lived: 370
Next birthday: Jun 15, 2026 — 49 days away

主な使用シーン

主な使用シーン

1. Verify exact age for legal or administrative purposes — visa applications, contracts, or insurance forms that require years, months, and days.

2. Calculate a child's age precisely for school enrollment or pediatric checkups.

3. Find out how many days until your next birthday to plan celebrations.

4. Satisfy curiosity about how many days or weeks you have lived.

5. Check whether someone has reached a specific age threshold on a given date.

よくある質問

よくある質問

How does the calculator handle leap years?v
The calculation uses actual calendar dates, so leap years are handled correctly. The day difference uses the real number of days between two dates, and the month/day decomposition adjusts for varying month lengths including February in leap years.
Can I calculate someone else's age?v
Yes. Simply enter their date of birth. The calculator always computes the age relative to today's date.
What format should I enter the date in?v
Use the browser's native date picker (calendar widget) for the easiest input. If typing manually, use YYYY-MM-DD format (e.g., 1990-03-25). The field accepts any valid date from past to today.
Why does the months count sometimes seem off by one?v
If your birthday hasn't occurred yet this month, the calculator correctly counts one fewer month. For example, if you were born on the 28th and today is the 15th, the current month is not yet complete and is not counted.