How this calculator works
Chinese nominal age, called xusui, counts the year of birth as the first year and adds one at each Chinese New Year, so it changes on the lunar New Year rather than on the birthday. Hijri age works differently: it expresses the elapsed days in Islamic lunar years, which average about 354.37 days rather than 365.24. The international age is included as the familiar reference point.
Formula
Chinese nominal age = reference year - birth year + 1 when the Chinese New Year has already occurred in the reference year, otherwise reference year - birth year. Hijri age = elapsed days / 354.367056. International age counts completed Gregorian birthdays.
Worked example
Born on 1990-05-20 and measured on 2026-11-01, after that year's Chinese New Year: international age is 36, Chinese nominal age is 37, and Hijri age is 13314 / 354.367056 = 37.6 lunar years.
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Frequently asked questions
Why is the Chinese age one year more than the international age?
Because the birth year counts as year one, and everyone adds a year at Chinese New Year. The difference is usually one year, and can be two just before the birth date in a calendar year.
Why is Hijri age higher than Gregorian age?
A lunar year is about 11 days shorter than a solar year, so more lunar years fit into the same number of days. The ratio is roughly 365.24 / 354.37, or about 1.03.
Does this page know the exact Chinese New Year date?
No. It uses your answer about whether the new lunar year has begun. Chinese New Year falls between January 21 and February 20, so near that window you need to check the date for the year in question.
Which age should I use on an official form?
Use the age required by the form's own rules. Most Canadian and international documents ask for date of birth or completed Gregorian years, not a lunar age. The lunar figures are cultural and comparative.