How Old Are You in Hijri Years? A Calculator and the Arithmetic of the Hijri Birthday

The Short Answer

A Hijri year lasts about 354.37 days. A Gregorian year lasts about 365.24 days. Every Gregorian year of your life is therefore 1.031 Hijri years, and you gain one whole extra year of age about every 32.6 years: you are one year older in Hijri years from about your 33rd birthday, two years older from about your 65th, and three from about your 98th.

A baby born on 1 January 2000, which was 24 Ramadan 1420, was 26 on 13 October 2026 and 27 in Hijri years. The calculator below does the same for your date of birth. It needs nothing but the date, and it does not store or send it.

How the Arithmetic Works

Convert by multiplying: Hijri years lived = Gregorian years lived x 1.03069. The 1.03069 is 365.2425 divided by 354.3667, where 354.3667 is the mean year of the tabular Hijri calendar (10,631 days in 30 years, the number behind the 11 leap years in 30). The Umm al-Qura table this page uses has almost the same average: its 80 years from 1420 to 1499 AH hold 28,349 days, which is 354.36 days a year.

Turned round, 100 Hijri years last only 97.02 Gregorian years.

Your age counts completed years, so these decimals are not your age: at 33 Gregorian years you have lived 34.01 Hijri years and are 34. And age is not the difference of the two year numbers. In the example the Hijri year is 1448 and the baby was born in 1420, but 1448 minus 1420 is 28, not 27. The year number changes at 1 Muharram, which in 2026 was in June, while the birthday, 24 Ramadan, is not until 3 March 2027. You are one year younger than the subtraction says until your birthday comes round, exactly as with the Gregorian calendar.

Why Your Hijri Birthday Keeps Moving

Your birthday comes round every 354 or 355 days, so each year it falls about 11 days earlier in the Gregorian calendar. For the baby born on 1 January 2000 the birthdays are 20 December 2000, 9 December 2001, and so on, 3 March 2027 for the 28th, 20 February 2028 for the 29th, 8 February 2029 for the 30th. Each dot in the figure is one of these birthdays: its Gregorian year across, the date within the year up.

After about 32.6 years the date has slid all the way round the year. In 2032 the birthday has reached 7 January, and the next one comes only 355 days later, on 27 December 2032, before the year is out: that Gregorian year holds two Hijri birthdays, the 33rd and the 34th. It happens again in 2065, on 1 January and 22 December. For anyone born in the Umm al-Qura table's range, a year with two Hijri birthdays comes about once every 33 years.

How Much of the Year Are You Older?

Between your Hijri birthday and your Gregorian one you are one year older in Hijri years than in Gregorian years. That window grows by about 11 days with every year of life. For the baby born on 1 January 2000 it lasts 23 days in the year they are 1, 120 days at 10, 294 days at 26 (nearly ten months) and the whole year from 33. Your Hijri age is never lower than your Gregorian age, whatever your date of birth, because every Hijri year is shorter than every Gregorian one.

Which Hijri Calendar?

Your Hijri date of birth depends on the calendar that names it. This calculator uses the Umm al-Qura table, the one on the calendar page. A purely arithmetical calendar, or a calendar that follows the sighting of the crescent in your country, can place the same day a day or two away, and then your birthdays move with it. The triple-engine post compares the three kinds, and the Umm al-Qura explainer describes the one used here.

For a birth before the year 2000 the Umm al-Qura calendars in common use do not agree with each other. We compared the table with the Umm al-Qura calendar built into JavaScript (the ICU library, which most browsers use) on every day from 1900 to 1999: they gave the same date on 19 per cent of the days, ICU gave a date one day earlier on 80 per cent and two days earlier on 1.4 per cent. From 1 January 2000 to 31 December 2028 they agree on all 10,593 days. So for an older birth the Hijri date of birth, and the Hijri birthdays, can differ by a day from a result worked out elsewhere. The calculator says so when you enter such a date.

The calculator covers 30 April 1900 to 16 November 2077, the span of the table. If you were born on day 30 of a month, and the month in the year in question has only 29 days, the birthday is counted on the last day of that month.

Which Age Counts?

This page gives the age. It does not say which age applies. Where a rule, a form or a contract is written in Hijri years, or in Gregorian ones, the authority that sets the rule decides which counts and which calendar defines the date, and that is the place to check.

Frequently Asked Questions

How do I work out my age in Hijri years without a calculator?

Multiply your exact age in Gregorian years, with the fraction, by 1.0307 and drop the decimals. Someone born on 1 January 2000 was 26.78 years old on 13 October 2026, and 26.78 x 1.0307 = 27.6, so 27. The method is only a guide, because the real Hijri years are 354 or 355 days rather than the mean: within a few days of a Hijri birthday it can be a year out, and only the dates settle it.

Why is my Hijri birthday on a different date every year?

Because the Hijri year has about 354 days and the Gregorian year 365. Each year your birthday falls about 11 days earlier in the Gregorian calendar, and it takes about 33 years to come back to the same date.

Can I have two birthdays in one Gregorian year?

Yes, about once every 33 years. If your Hijri birthday falls in the first days of January, the next one comes about 354 days later, before the year ends. For someone born on 1 January 2000 it is 2032.

Is my Hijri age ever lower than my Gregorian age?

No. Every Hijri year is shorter than every Gregorian year, so you reach each Hijri birthday sooner than the matching Gregorian one.

Does the calculator use my time zone or my location?

No. It works on calendar dates, so the result for a date is the same wherever you are, apart from "today", which is the date on your device. The Umm al-Qura calendar is a single table for everyone; it does not follow the Moon in your own sky. See the triple-engine post for calendars that do.

See Also

• Why the Hijri calendar has 11 leap years in 30
• When will the Hijri year match the Gregorian year?
• Which years have two Eids?
• The Umm al-Qura calendar explained
• How the Islamic lunar calendar works
• The calendar page, to see any date in the three calendars.

References

• The numbers and the charts in this post are reproduced by docs/research/hijri-age.mjs, and computed by packages/astronomy/src/hijriAge.ts, in the Hilal Vision source.
• The Umm al-Qura table is the one in the @umalqura/core library, which covers 1318 to 1500 AH (30 April 1900 to 16 November 2077).