Age Calculator
Your exact age in years, months and days — plus total days and next birthday.
What is Age Calculator?
Age Calculator gives your exact age in years, months, and days from your date of birth — plus the same span as total months, weeks, and days, and a countdown to your next birthday. The reference date defaults to today but can be any date, so you can calculate age on a future event. Free, and it runs in your browser.
Key features
- Exact age in years, months, and days
- Totals: months, weeks, and days lived
- Days remaining until your next birthday
- Age at any reference date, not just today
- Leap years and month-end dates handled correctly
Age Calculator — exact age from date of birth
Most "how old am I" answers stop at the year. This tool gives the full figure — years, months, and days — from a date of birth to today or any date you choose, then restates that same span as total months, weeks, and days and counts down to your next birthday. It's the version you want for a form that asks for age in months, a milestone post, or working out someone's age on a specific future day.
How the years / months / days figure is worked out
Age isn't a plain subtraction, because months have different lengths. The calculator counts down from years to days and borrows whenever a field would go negative: if the day you were born on hasn't come around yet this month, it takes the length of the previous calendar month — 28, 29, 30, or 31 days as appropriate — and drops the month count by one. That borrowing is exactly what keeps the answer correct across month ends and leap years, instead of pretending every month is 30 days.
So someone born on the 31st, measured during a month that only has 30 days, gets the true remaining days rather than a rounding slip.
Totals and the birthday countdown
Below the headline figure, the same lifetime appears in three single units:
- Total months — years × 12 plus the leftover months; useful for baby ages or subscription anniversaries.
- Total weeks — whole weeks only, the day count divided by seven and rounded down.
- Total days — every day lived, the number behind "10,000 days old" milestones.
- Next birthday — how many days remain until the anniversary of your birth date.
Age at any reference date
The reference ("as of") date defaults to today but is fully editable. Push it into the future to see how old you'll be at a wedding or graduation; pull it back to check an age at a past event. The one rule the tool enforces is that the reference date must fall on or after the birth date — a birth date in the future returns an "invalid" notice rather than a negative age.
Things worth knowing
- All arithmetic uses UTC calendar dates, so the day count never shifts because of a time zone or a daylight-saving change.
- A 29 February birthday is measured against the real length of February in the year in question, so common years resolve to the correct day.
- Everything runs in your browser; the birth date you type is never uploaded.
- For Korea's 만 나이, which counts age differently, use the dedicated Korean Age Calculator — this tool follows the standard international method.
Frequently asked questions
- Can I set the reference date to a future day?
- Yes. The "as of" field defaults to today but accepts any date, so you can see you'll be, say, 42 years, 3 months, 12 days old on a specific wedding day. It only refuses when the reference date falls before the birth date, which it flags as invalid rather than showing a negative age.
- How does it handle a February 29 birthday?
- It measures against the real length of February in the year you're checking, so the day count stays correct. In common years there is no Feb 29, so the months and days resolve to the nearest valid day instead of breaking.
- What's the difference between the years/months figure and "total months"?
- The headline is calendar age like "31 years, 2 months, 5 days"; total months collapses that to one number (years times 12 plus months, so 374 months). Total weeks and total days do the same from the full day count, which is what powers "10,000 days old" style milestones.
- Why can the day count differ from a quick mental subtraction?
- Because months aren't all 30 days. When your birth day-of-month hasn't arrived yet this month, the tool borrows the previous month's actual length (28 to 31 days), which is exactly what a naive "times 30" estimate gets wrong around month ends and leap years.
- Does this give Korean age (만 나이)?
- No, this uses the standard international method. For Korea's 만 나이, which counts age differently, use the dedicated Korean Age Calculator instead.
Privacy
The date arithmetic runs locally in your browser; your birth date is never sent to a server.