You’ve probably heard a specific number thrown around in biology class or on social media. Maybe it was 1.7%. Or maybe you heard it’s so rare you’ll never actually meet someone who fits the description. Honestly, the reality is a bit messier than a single decimal point. When people ask what percent of the population is intersex, they usually want a simple answer. But "intersex" isn't a single medical condition. It's an umbrella. It covers everything from chromosomal variations like XXY to hormonal differences that might not even be noticed until someone tries to have a baby in their 30s.
It’s complicated.
Breaking Down the 1.7% Figure
Let’s talk about that 1.7% stat. It’s the one everyone cites. It comes primarily from Dr. Anne Fausto-Sterling, a professor at Brown University. Back in 2000, she and her colleagues reviewed decades of medical data to figure out how many people don't fit the "standard" male or female mold. They landed on 1.7. To put that in perspective, that’s about the same number of people born with red hair.
If you’re sitting in a crowded coffee shop right now, odds are someone there is intersex. They just might not know it.
However, not every scientist agrees with that math. It really depends on how you define the term. If you use a very strict medical definition—only including people where their external genitals don't match their internal genetics at birth—the number drops significantly. Dr. Leonard Sax, a psychologist and physician, argued in 2002 that the "true" intersex rate is closer to 0.018%. That's a huge difference. Why the gap? Sax argues that conditions like Late-Onset Congenital Adrenal Hyperplasia (LOCAH) shouldn't count because they don't always result in "ambiguous" physical traits.
But for the person living with the condition, those distinctions feel kinda arbitrary.
The Varieties of Intersex Experiences
We aren't just talking about one thing here. It’s a spectrum. Some people have Klinefelter syndrome (XXY). This affects roughly 1 in 500 to 1,000 biological males. Most of them go their entire lives without realizing they have an extra chromosome. They might just be tall or have slightly less body hair. Then you have Turner syndrome (X0), which affects about 1 in 2,500 biological females.
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Then there is Androgen Insensitivity Syndrome (AIS).
Imagine growing up as a girl, looking like every other girl, and then finding out during puberty that you have XY chromosomes and internal testes. This isn't a sci-fi plot. It's the reality for about 1 in 20,000 people. Some have "complete" AIS, meaning their bodies don't respond to testosterone at all. Others have "partial" AIS, which can lead to a mix of physical traits.
- Congenital Adrenal Hyperplasia (CAH): This is the most common cause of intersex traits in people with XX chromosomes.
- 5-alpha reductase deficiency: A rare condition where individuals are often raised as girls but develop male physical characteristics during puberty.
- Chimerism: This is incredibly rare, where a person has two different sets of DNA, often because two embryos fused in the womb.
Why the Numbers Keep Changing
Statistics are slippery. In many parts of the world, intersex variations are still treated as "medical emergencies" to be fixed with surgery immediately after birth. When a doctor performs a corrective surgery on an infant, that child might grow up never knowing they were born with an intersex trait. Their medical records might just say "hernia repair" or something equally vague.
Because of this secrecy, it's basically impossible to get a perfect headcount.
We also have to consider that "intersex" is a social and political identity as much as a medical one. Many people with chromosomal variations don't identify as intersex. They just see themselves as a man or a woman with a specific health condition. Others embrace the term to find community and advocate against unnecessary childhood surgeries.
If we only count people who identify as intersex, the percentage would be tiny. If we count everyone whose biology deviates from the XX-female/XY-male binary, the number climbs back toward that 1.7% mark.
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The Medicalization of Bodies
For a long time, the medical community used the term "hermaphrodite." We don't use that anymore; it's considered stigmatizing and scientifically inaccurate. In 2005, a group of doctors gathered in Chicago and proposed a new term: Disorders of Sex Development (DSD).
This change was controversial.
Advocates hated the word "disorder." They felt it suggested that their bodies were "broken" rather than just diverse. Yet, many parents preferred the medicalized term because it made the situation feel like something a doctor could manage. This tug-of-war over language is why you’ll see different percentages in different studies. A study looking for "DSDs" might find different data points than one looking for "intersex variations."
What Science Says in 2026
Recent genetic sequencing is showing us that biological sex is much more of a "bimodal distribution" than a strict binary. Think of two mountains with a valley in between. Most people are on one of the two peaks, but plenty of people are hanging out in the valley or on the slopes.
Research from the Intersex Society of North America and newer genomic studies suggest that as our ability to test DNA improves, we’re finding more "micro-variations." We’re discovering that some men have a small percentage of XX cells, and some women have XY cells, a phenomenon known as microchimerism.
Does this make them intersex? By the broadest definition, maybe.
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The Human Side of the Data
Stats are cold. They don't tell you about the teenager who feels like an alien because they aren't hitting puberty like their friends. They don't tell you about the adult who discovers their infertility is actually due to a chromosomal variation they never knew existed.
Take the case of Caster Semenya, the Olympic runner. Her body naturally produces high levels of testosterone. The sports world didn't know how to handle her. They forced her to take medication to lower her hormones to "standard" female levels. This sparked a global debate: where do we draw the line? If someone is born with a natural biological advantage, why is it treated as a "disorder" only when it relates to sex?
We don't tell basketball players they are "too tall" and need surgery to be shorter.
How to Support the Intersex Community
If you’re looking at these numbers because you want to be a better ally, the best thing you can do is move past the "rarity" argument. Whether it's 1.7% or 0.018%, we are talking about millions of human beings.
- Respect Self-Identification: Let people use the terms they are comfortable with, whether that’s intersex, DSD, or just their specific diagnosis.
- Educate Others: Most people still think sex is purely XX or XY. Sharing the fact that there are at least six common biological sex karyotypes can change how people view the world.
- Advocate for Bodily Autonomy: Many intersex organizations, like interACT, work to end non-consensual surgeries on infants. The goal is to let the individual decide what happens to their body when they are old enough to give consent.
Moving Forward With the Facts
When you’re trying to pin down what percent of the population is intersex, remember that the "truth" is a moving target. The 1.7% figure remains the most widely accepted estimate for broad biological variations, but the medical reality is nuanced.
The most important takeaway isn't the number itself. It’s the realization that human biology is incredibly diverse. We’ve tried to cram everyone into two boxes for centuries, and it just doesn't work for everyone.
Next Steps for Deeper Understanding
- Audit your language: Start using "assigned male/female at birth" rather than "born a boy/girl" when discussing these topics to acknowledge the medical assignment process.
- Follow Intersex creators: Look for activists like Pidgeon Pagonis or Hans Lindahl who share lived experiences that provide context beyond the clinical data.
- Check the sources: If you see a new statistic, look at the criteria. Did they include LOCAH? Did they include Klinefelter? The "who" determines the "how many."
- Support Policy Changes: Look into local and national legislation regarding "standard of care" for intersex infants to ensure medical practices align with modern human rights standards.
The data will continue to evolve as genetic testing becomes a standard part of healthcare. We are likely to find that we are all a little more complex than we originally thought.