Age calculator: compute your exact age in years, months, and days from any birth date, plus days until your next birthday. Free, runs in your browser.
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Calculation details
Every figure above is calculated locally in your browser from the assumptions shown. No inputs are sent anywhere. See the methodology section below for how this tool works.
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Planning estimate only, not financial, tax, or legal advice. Verify assumptions and current rules before making decisions.
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This age calculator instantly computes your exact age in years, months, days, weeks, and hours from your date of birth. It calculates calendar age by subtracting complete years, then complete months, then remaining days, and uses UTC date boundaries for total days so daylight-saving shifts never affect the result. Use the output to confirm your precise age for forms, milestones, or any date-based planning.
13,248 days resolve to 36 years, 3 months, 7 days.
Formula & evidence
How this calculator works
Reviewed July 2026 · BoringToolsKit Editorial Team
Formula
Calendar age counts complete years, then months, then days between birth date and the as-of date; totals convert elapsed days to hours and weeks.
Worked example
Born June 15, 1990, as of July 13, 2026: 36 years, 0 months, 28 days, or 13,177 days elapsed.
Sources support the method, terminology, or planning context. Editable assumptions remain your responsibility.
Assumptions to verify
Dates use the proleptic Gregorian calendar implemented by the browser.
Total weeks are total days divided by seven and may be fractional.
Legal age rules for leap-day birthdays can vary by jurisdiction.
Frequently asked questions
What is an age calculator?
An age calculator is a free online tool that instantly computes your exact age in years, months, days, weeks, and hours based on your date of birth.
Does this age calculator store my personal data?
No. This age calculator runs entirely in your browser and requires no signup or account. Your date of birth is processed locally and never sent to any server.
How accurate is the age calculator?
The age calculator is highly accurate, using your exact birth date and the current date to compute your precise age down to the day.
BoringToolsKit. “Age Calculator.” boringtoolskit.com/age-calculator/ (reviewed July 2026). Free to reference in articles, syllabi, and answer posts with a link.
Privacy: Inputs and results stay in this browser. Results are planning estimates based on your inputs; verify assumptions and current rules before making decisions.
A worked example, step by step
Set the birth date to 1990-06-15 and the calculation date to 2026-09-22. The calculator first counts whole years: 2026 minus 1990 is 36, and the candidate anniversary 2026-06-15 falls on or before the calculation date, so 36 years stands. It then counts whole months from that anchor: 2026-07-15, 2026-08-15, and 2026-09-15 each stay at or before 2026-09-22, but adding a fourth month would reach 2026-10-15, which overshoots. That gives 3 months.
The remaining days come from the last anchor: September 15 to September 22 is exactly 7 days, so the headline reads 36 years, 3 months, 7 days. Cross-checking the totals confirms it: 13,248 elapsed days equals 1,892.6 weeks and 36.27 years at 365.25 days per year, which matches 36 full years plus 3 months and a week.
The same inputs produce 266 days until the next birthday (June 15, 2027). Because the default birth and calculation times are both midnight, elapsed hours equal 13,248 days times 24, or 317,952.0 hours. Entering a birth time of 14:30 would add 14.5 hours, showing up as 317,966.5 in the hours metric.
Edge cases the calendar arithmetic has to survive
February 29 birthdays are the sharpest case. A person born 1992-02-29 has no anniversary in non-leap years, so on 2026-02-28 the count must stop at 33 years, 11 months, 30 days rather than rounding up to a 34th birthday one day early. The calculator handles this by clamping month arithmetic to each month's real length: adding one month to 2026-01-29 lands on 2026-02-28, the last valid day of February, not March 1.
Month-end dates behave the same way. One month after 2026-01-31 is 2026-02-28, and one month after 2026-08-31 is 2026-09-30, so ages measured from the 29th, 30th, or 31st compress at short months instead of spilling into the next month.
Time handling has its own limits. The tool assumes both dates are in the browser's local timezone, so a birth moment of 1990-06-15 23:30 in one timezone and a calculation moment across a daylight-saving shift can differ by an hour from a UTC-based count; fractional hours in the total are the giveaway. It also cannot represent historical calendar reform: dates before a jurisdiction switched from the Julian to the Gregorian calendar (Britain and its colonies in September 1752, which skipped 11 days) are measured as plain Gregorian days, so ages spanning that boundary will not match documents written at the time.
