How Rare Is
Your Birthday?
Enter your birth date and instantly discover how rare or common it really is — based on 100+ years of real global birth statistics.
Four Simple Steps
Getting your birthday rarity score takes less than 10 seconds. No sign-up, no personal data stored.
Choose your birth month and day. Adding your year gives extra details like your age and day of the week you were born.
Our algorithm cross-references your date against 100+ years of global birth statistics from CDC records and academic research.
Receive your rarity classification (Ultra Rare to Very Common), a score out of 100, worldwide population estimate, and key insights.
Share your rarity score with friends and family using the Share button, or copy a direct link to your result with one click.
A Complete Birthday Analysis
Your result is not just a number. It is a full breakdown of what makes your birthday unique — or surprisingly common.
Your birthday receives a score from 0 to 100 and a classification: Ultra Rare, Rare, Uncommon, Common, or Very Common.
Find out approximately how many people worldwide share your exact birthday, based on real demographic data.
See how your birthday ranks among all 366 possible calendar dates by birth frequency — top 10 most common or rarest 10.
Your zodiac sign is automatically detected from your birth date and displayed alongside your rarity score.
We calculate exactly how many days remain until your next birthday. If today is your birthday, we celebrate with you.
Seasonal birth patterns, holiday effects, the day of the week you were born, and what all of this means statistically.
Birthday Rarity Classifications
Every birthday falls into one of five categories based on relative birth frequency.
Most Common and Rarest Birthdays
Rankings derived from birth certificate data and demographic studies spanning multiple decades and countries.
| # | Date | Share | Tier |
|---|---|---|---|
| 1 | September 9 | 0.37% | Very Common |
| 2 | September 19 | 0.36% | Very Common |
| 3 | September 12 | 0.36% | Very Common |
| 4 | September 17 | 0.35% | Very Common |
| 5 | September 10 | 0.35% | Very Common |
| 6 | July 7 | 0.34% | Very Common |
| 7 | August 11 | 0.34% | Very Common |
| 8 | September 20 | 0.34% | Very Common |
| # | Date | Share | Tier |
|---|---|---|---|
| 1 | February 29 | 0.07% | Ultra Rare |
| 2 | December 25 | 0.18% | Rare |
| 3 | January 1 | 0.19% | Rare |
| 4 | December 24 | 0.19% | Rare |
| 5 | July 4 | 0.20% | Rare |
| 6 | November 27 | 0.21% | Rare |
| 7 | December 26 | 0.21% | Rare |
| 8 | January 2 | 0.22% | Rare |
Source: CDC birth data, Harvard School of Public Health research, and international birth statistics. Values are approximate.
Why Are Some Birthdays Rarer Than Others?
Birth rates are not evenly distributed across the 365 days of the year. Several well-documented factors explain the patterns we see in the data.
Planned Deliveries and Inductions
Modern medicine allows for scheduled C-sections and induced deliveries. Doctors and parents tend to avoid major public holidays, which significantly reduces birth rates on dates like Christmas Day and New Year's Day.
Seasonal Conception Patterns
Birth rates follow predictable seasonal cycles. Conceptions peak around the winter holidays, meaning September and October consistently have the highest birth rates each year.
The Leap Day Effect
February 29 only exists every four years, making Leap Day birthdays mathematically about four times rarer than any other date. This makes Leap Day the definitive Ultra Rare birthday.
Geographic and Cultural Factors
Birth rate patterns differ across countries and cultures. Religious observances, national holidays, climate, and cultural preferences all influence when people tend to have children.
Frequently Asked Questions
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