Why is my Hijri age greater?
Because age counts how many time cycles have passed, and the Hijri cycle is shorter than the Gregorian one. The Hijri year is lunar: twelve months, each beginning with a new crescent, totalling 354 days in a common year and 355 in a leap year. The Gregorian year is solar, fixed at roughly 365 or 366 days. The difference of about 11 days a year accumulates: after 33 Gregorian years the lunar months have completed 34 full turns, so your Hijri age is about a year greater. This is why many people are surprised to read in an official document that their Hijri age exceeds their usual age by a year or two — both numbers are correct; the days you have lived are the same, only the measure counting them differs.
The effect grows with age: a ten-year-old in Gregorian is about ten years and four months in Hijri; a man of sixty has completed about 62 Hijri years. Milestones tied to Hijri age — a retirement age calculated in Hijri, for instance — therefore arrive earlier than expected, which matters for long-term planning.
How age is calculated exactly (years/months/days)
An exact calculation does not divide the number of days by 365 or 30. It proceeds step by step: whole years up to the last birthday, then whole months up to the last monthly anniversary, then the remaining days. Because month lengths change from month to month and year to year, a "whole month" is measured by the actual month itself: someone born on 31 January reaches their first month at the end of February (the 28th or 29th), under the "last day of the month" rule. Our tool applies this logic twice — with Gregorian months, and with Hijri months exactly as the Umm al-Qura table sets them, since Ramadan is 30 days in one year and 29 in another.
A fully worked example: a baby born on 1 Ramadan 1447 AH, corresponding to 18 February 2026 CE, whose age we calculate on 28 Jumada al-Ula 1448 AH, corresponding to 8 November 2026 CE. In Gregorian: from 18 February to 18 October is eight whole months, and from 18 October to 8 November is 21 days, so the age is 8 months and 21 days. In Hijri: from 1 Ramadan 1447 to 1 Jumada al-Ula 1448 is eight whole months, and from 1 Jumada al-Ula to the 28th is 27 days, so the age is 8 months and 27 days. The baby has actually lived 263 days either way — the day does not change with the calendar, only its grouping into years and months. The tool above shows exactly these figures — including the baby's first Hijri birthday, 1 Ramadan 1448, falling on 8 February 2027.
Why a Hijri birthday sometimes falls twice in one Gregorian year
Because a Hijri birthday returns every 354 days on average while the Gregorian year is 365 days, its date advances about 11 days each year through the Gregorian calendar, until it crosses the boundary of the Gregorian year. In one Gregorian year a person may celebrate a Hijri birthday in January and the next in December — two Hijri birthdays in a single Gregorian year. This happens roughly once every 33 years, matched by years with no Hijri birthday at all, when the date jumps from late December past the next year's end. That is why the tool shows your next birthday in both calendars with a countdown: planning by a fixed Gregorian date ("next March") leads to error unless that year's corresponding Hijri date is checked.
Hijri age for official transactions (retirement, schools)
In Saudi Arabia and much of the Gulf, Hijri age is no side detail: it is the birth date recorded in the documents of whole generations, and many systems still calculate entitlements by it. School enrolment ages are set by a Hijri limit in some authorities, retirement and end-of-service entitlements for some categories are calculated in Hijri years, and document renewal dates may appear in both calendars. A common office mistake is converting age with approximate formulas (such as multiplying the Gregorian age by 1.03), producing differences of whole months. The correct method is to convert the birth date itself from the Umm al-Qura table and then recalculate the age on the real Hijri months — which is what this tool does automatically.
Practical advice: if asked for your Hijri age, give your Hijri birth date as shown above and let the authority calculate where needed. The date is fixed and undisputed, whereas an age in months and days changes daily, and authorities differ in their reference day (application day, school-year start, or entitlement date).