Your Hijri birthday, and your age in Islamic years

Two ages, both correct

Take someone born on 15 March 1995. In the Umm al-Qura calendar that day is 14 Shawwal 1415 AH. On 12 August 2026 they have been alive for exactly 11,473 days, and that single day count can be expressed in either calendar's units.

In Gregorian units it comes to 31 years, 4 months and 28 days. In Hijri units the same 11,473 days come to 32 years, 4 months and 15 days. Neither number is rounded and neither is an approximation; they simply measure the same span with different-sized years.

The calculator arrives at the Hijri figure the way you would by hand: it converts the birth date and the target date to their Hijri equivalents and subtracts years, months and days. When the day subtraction goes negative it borrows one month, adding back the real length - 29 or 30 days - of the Hijri month before the target date, taken from the calendar table rather than an average. When the month subtraction goes negative it borrows twelve months from the years. That borrow rule is why the months-and-days part of the answer is exact and not just the day count divided by twelve.

Where the extra year comes from

Divide those 11,473 days by the average length of each calendar's year and the gap explains itself. At 365.24 days per Gregorian year the span is 31.4 years; at 354.37 days per Hijri year it is 32.4. Same days, shorter ruler, bigger number.

The rate is easy to remember. The Hijri year runs about eleven days shorter than the Gregorian year, so the difference between your two ages grows by about eleven days every year. After roughly 33 Hijri years - which is roughly 32 Gregorian years - those eleven-day slices add up to one whole extra year. A 32-year-old has a Hijri age of about 33; a 64-year-old is around 66 in Hijri years; by a Gregorian 96 the Hijri count reaches about 99.

Nothing in this is specific to birthdays. Any duration measured in Hijri years comes out about 3 percent larger than the same duration in Gregorian years, for the same reason a distance in kilometres is a bigger number than the same distance in miles.

Your Hijri birthday moves through the Gregorian year

A Hijri birthday is the same idea as a Gregorian one: the day and month of birth, observed each time the calendar comes back around to them. For the person born 15 March 1995, that day is 14 Shawwal. The catch is that the Hijri year is shorter, so 14 Shawwal returns 10 to 12 days earlier in the Gregorian year every single time.

Here are five consecutive Hijri birthdays for that birth date, from the Umm al-Qura calendar. The drift is the same eleven-day slide that moves every other Hijri date, and the weekday changes each year as well.

Watched over a lifetime, the Hijri birthday makes a complete lap of the Gregorian calendar: from mid-March back through winter, autumn and summer, and eventually into March again. A birthday that starts in spring will, in the space of a decade and a half, be a winter date.

Roughly once every 33 years, the two birthdays meet

Because the Hijri birthday moves about eleven days earlier each year, and there are about 365 days of Gregorian calendar for it to move through, it comes back to the neighbourhood of the original date after about 33 Hijri years. The two birthdays then fall within days of each other, once, before the drift carries them apart again.

The example shows it neatly. The 33rd Hijri birthday of someone born 15 March 1995 is 14 Shawwal 1448, which the Umm al-Qura calendar places on 22 March 2027 - exactly one week after their 32nd Gregorian birthday. For a few years around that point the two anniversaries crowd together in the same month; a generation later they are half a year apart.

This is the same 33-year cycle that governs the whole calendar, and the guide on how the Islamic calendar works walks through it in full. Applied to ages it gives the rule of thumb from earlier in this guide: the Hijri age pulls one year ahead every 32 to 33 Gregorian years.

The edge cases that trip people up

Most birth dates convert cleanly, but three situations produce answers that look wrong and are not.

• Born on the 30th of a Hijri month. Hijri months are 29 or 30 days, and the same month changes length from year to year. 30 Dhu al-Hijjah 1445 exists - it was 6 July 2024 - but in 1446 the month stopped at 29 days, so that anniversary simply has no matching day in some years, exactly like a 29 February birthday.
• The calendars disagree about the birth date itself. 15 March 1995 is 14 Shawwal 1415 under Umm al-Qura but 13 Shawwal 1415 under the tabular civil calendar. Both are correct within their own system, which is why the calculator lets you choose the calendar and why a Hijri date should always be quoted with its calendar named.
• Born before the table opens. The embedded Umm al-Qura data begins at 1 Muharram 1318 AH, which is 30 April 1900. For a birth date earlier than that, the Umm al-Qura engine has no answer; switching the calculator to the tabular calendar gives one, because the tabular rule is pure arithmetic and is defined for any year.
• All of these dates are civil calculations. A date recorded from a local announcement at the time of birth can differ by about a day from what any calculated calendar shows.

Getting the number, and keeping it

The age calculator on this site takes a Gregorian birth date and any target date, shows the age in Hijri years, months and days alongside the total day count, and lets you switch between the Umm al-Qura and tabular calendars to see how much the choice matters. The converter does the same for a single date in either direction.

If you want to keep the result, the My Dates page stores a personal date - a birthday, an anniversary - and shows it in both calendars whenever you come back. And if the drift itself is the interesting part, each Hijri month page explains what its month contains, and every Hijri year page shows exactly how long each year ran.

Frequently asked questions