Fuzzy Math: Why the ‘Sex Calculator’ Is a Harmful Gimmick

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Commentary Sexual Health

Fuzzy Math: Why the ‘Sex Calculator’ Is a Harmful Gimmick

Martha Kempner

The old trope of "you've had sex with everyone your partner has had sex with and everyone their partners had sex with" got a fancy website this week. But the math is useless, unless your goal is to shame someone for their sex life.

The first time I heard the theory that when you have sex with one person, you have sex with everyone they’ve ever had sex with, and everyone they’ve ever had sex with, ad infinitum, I was a freshman at the University of Massachusetts watching a performance of the “Not Ready for Bedtime Players.” The campus health education theater troupe did a skit featuring a couple in bed whose first time together got more and more awkward as former partners, and partners of partners, kept showing up and demanding room under the covers.

At the time, I thought the concept was kind of funny. But as the years went on and I kept seeing this idea put forth over and over, I began to realize that it’s less about risk assessment and more about making people feel bad for having slept with “too many” people.

The most frequent employers of this trope are those teaching “abstinence-until-marriage” sex ed curricula. Now, though, it’s gotten new legs: In honor of the United Kingdom’s Sexual Health Week, the famous British pharmacy Lloyd’s has launched an online sex calculator. Though the pharmacy insists the goal of the “Sex Degrees of Separation” website is to promote the importance of condom use and frequent STI testing, once again, I think it all comes down to slut-shaming.

The calculator asks you whether you have slept with men, women, or both. It then asks how many partners you’ve had, and their age when you had sex with them. The behind-the-scenes math is apparently based on data about the average number of partners people in the UK have had by the time they reach a certain age. It uses that data to calculate how many partners your partners (and up to five of their partners) have likely had, and you get to watch as those numbers add up fast.

Sex. Abortion. Parenthood. Power.

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There are plenty of problems with this tool. First off, it’s far from precise—there’s a lot of guessing and estimating that has to take place. Take my own answers as an example. I’m in the United States, where the numbers of average partners are likely at least a little different. Plus, the partners I marked were between the ages of 16 and 19 around 1990, which means the averages are a quarter of a century off.

Of course, my biggest challenge with finding my own magic number was how to categorize my husband. He was 23 when I met him but we were still together when he hit 25, married when he was 35, and will (I presume) still be hanging out when he gets to 44—all of which is associated with a different average number of partners. Ultimately, I wound up marking him as 23, because that’s when he presented the highest STI risk for me, a new partner at the time.

According to the calculator, I’ve “slept” with 2,311,704 people.

However, I have only slept with one of them in the last two decades. Plus I’ve been tested for STIs multiple times over those years. The calculator may be meant as an STI risk-assessment tool, but my number, combined with my 20-year monogamous relationship, points to an unmistakable fact: It’s meaningless. It is telling me nothing about my current risk.

STI risk is not all equal, nor is it necessarily cumulative. The idea of sleeping with everyone your partner is sleeping with is most true for people who have more than one sexual partner at the same time. Though even then, it’s fuzzy math at best. If those partners are getting frequent STI tests and using condoms regularly, the risk goes way down. And for those practicing serial monogamy, a battery of STI tests before having sex with a new partner can wipe the slate pretty much clean, and kick all of those former partners out of the “bed.”

When the calculator returns your number, the Lloyd’s website suggests channeling your shock into a test and gives some resources on where you can go. STI testing is hugely important both in treating those who are infected and preventing others from becoming infected. Despite its noble goal, however, I think the gimmick of the calculator indicates a harmful trend. The numbers go up so fast that a person who says they’ve had only one male partner who was between the ages of 16 and 19, is told they’ve actually had sex with 137,548. Such math is clearly irrelevant to calculating that person’s risk of STIs (which is pretty low) and can only serve to make her or him alarmed at how theoretically promiscuous they are. This may compel some people to take testing measures, sure, but it feeds into a narrative that makes people ashamed of their sexual behavior.

This trope has historically been used to suggest people have fewer sex partners. While it is often done under the guise of limiting STI risk, it sends a pretty clear message of potential disapproval. In the case of the abstinence-only-until-marriage curricula that I’ve read, for example, it was designed to say that any more than one partner was too many not just because you would inevitably get an STI, but because your sex life would be plagued by flashbacks of former lovers.

Though this is an extreme limit (with absurd logic behind it), everyone does seem to have their own opinion on what is an acceptable number of sexual partners to have had over the course of a year, by the time you get married, or in your lifetime. In general, that number tends to be under the two million mark. The mere act of counting at all, though, suggests that at some point people will inevitably cross that line from acceptable to “slut.”

Casting disapproval over someone’s behavior is rarely an effective way to get them to take care of their sexual health. Straightforward messaging about testing frequently and before every new partner (regardless of whether it’s your second or your two millionth) would be a better tactic, and not one that requires any fancy calculations.

CORRECTION: This article has been updated to clarify the mechanisms of the “sex calculator.”