Age Calculator

How to use this tool

Enter a Date of Birth and an Age at the Date of target (which defaults to today's date), then click Calculate to view the exact age in years, months, and days, along with total months, total weeks, and total elapsed calendar days. All date inputs stay strictly inside your browser tab.

To count total workdays or calendar days between two arbitrary project dates, use the Days Between Dates Calculator or Business Days Calculator.

To add or subtract a specific number of years, months, or days from a date, use the Date Calculator.

Transparent method: how chronological age is calculated across unequal months

This calculator uses its documented completed-year, completed-month, and remaining-day convention. It is a general calendar tool, not an eligibility decision for legal, medical or benefit purposes:

Completed Years: Increases by 1 each time you reach your birth month and birth day in a new calendar year.

Completed Months: Counts how many full monthly anniversaries of your birth day have passed since your most recent birthday.

Remaining days (calendar-anniversary method): After counting completed years and months, the calculator counts days from the last clamped monthly anniversary to the comparison date. Month lengths follow the Gregorian leap-year rules.

Worked example of the calendar-anniversary method

Suppose a child was born on January 20, 2024 and you want their exact age on March 5, 2026:

Years: From January 20, 2024 to January 20, 2026 = 2 completed years.

Months: From January 20, 2026 to February 20, 2026 = 1 completed month.

Days: From February 20, 2026 to March 5, 2026: because 2026 is a common year where February has 28 days, there are 28 − 20 = 8 days remaining in February plus 5 days in March = 13 days.

Exact chronological age: 2 years, 1 month, and 13 days (or 775 total elapsed days, which includes Leap Day on February 29, 2024).

Quick-reference table: birth year to age in 2026 (Before vs. After Birthday)

Use this lookup table for ordinary birthdays in 2026. Check legal eligibility separately against the applicable authority.

Leap-day birthdays and calendar conventions

A Gregorian leap year is divisible by 4, except a century year must also be divisible by 400. This calculator uses its documented February 28 convention for a February 29 birthday in a non-leap year. Legal or benefit rules may use a different convention; check the governing authority before relying on a threshold.

How to calculate exact age in Microsoft Excel and Google Sheets (DATEDIF)

To calculate a person's exact age in Years, Months, and Days inside Excel or Google Sheets (assuming their Date of Birth is in cell A2), use the built-in Microsoft Excel DATEDIF function:

The spreadsheet examples use October 27, 2026 as a fixed comparison date. Microsoft warns that DATEDIF with the MD argument can produce inaccurate results in some cases. Check end-of-month boundaries. Calendar hours in this tool are calendar days × 24, not elapsed wall-clock hours.

Assumptions and limits

• The birth date cannot be later than the comparison date.
• Dates are evaluated as calendar dates without time-of-day or timezone offsets.
• A February 29 anniversary is treated as February 28 in a non-leap year; legal treatment can vary by jurisdiction.

Sources

• DATEDIF Function — Calculate the Number of Days, Months, or Years Between Two Dates
• Leap Years — Astronomical Applications Department