Published in


What Are the Chances of Finding Love?

An excerpt by Hannah Fry

Love, as with most of life, is full of patterns — from the number of sexual partners we have in our lifetime to how we choose who to message on a dating website. As mathematician Hannah Fry aptly and amusingly demonstrates in her new TED Book, The Mathematics of Love, math is a surprisingly useful tool for negotiating the complicated, often baffling, sometimes infuriating, always interesting patterns of love. Be warned: while reading this, you might just fall in love…with math.

For those of us who have been single for any length of time, finding someone special can sometimes feel like an insurmountable challenge. A few years of dating a succession of boring Bernards and psycho Suzys can leave us frustrated, disappointed, and feeling like the odds are stacked against us. And some people will tell you that your feelings aren’t necessarily unfounded. In fact, in 2010, mathematician and long-standing singleton Peter Backus even calculated that there were more intelligent alien civilizations in the galaxy than potential girlfriends for him to date.

But things might not be as hopeless as they initially appear. There are 7 billion people on Earth after all, and while not all of them will be to our particular taste, this chapter explains how we can use Backus’ method to calculate your chances of bagging yourself a partner — and specifically, why being a bit more open to potential will give you a better chance of finding love on your own planet.

In Backus’ paper (titled “Why I Don’t Have a Girlfriend”), he adapts a formula used by scientists to consider why Earth hasn’t yet been visited by aliens to instead work out how many women would meet his criteria for a girlfriend.

The formula exploited a trick well known to scientists of breaking down the estimation by making lots of little educated guesses rather than one big one. The result of this trick is an estimate likely to be surprisingly close to the true answer, because the errors in each calculation tend to balance each other out along the way. Depending on the values chosen at each of the steps (and there is some debate over the final few), scientists currently think there are around 10,000 intelligent extraterrestrial civilizations in our galaxy. This is not science fiction: scientists really have convinced themselves that there is life out there.

Of course, just as it’s not possible to calculate precisely how many alien life-forms there are, it’s also not possible to calculate exactly how many potential partners you may have. But all the same, being able to estimate quantities that you have no hope of verifying is an important skill for any scientist.

This technique applies perfectly to Peter Backus’ quest to see if there are intelligent, socially advanced women of the same species out there for him to date. And the idea is the same: break the problem into smaller and smaller pieces until it’s possible to make an educated guess. These were Backus’ criteria:

  1. How many women are there who live near me?
    (In London -> 4 million women)
  2. How many are likely to be of the right age range?
    (20% -> 800,000 women)
  3. How many are likely to be single?
    (50% -> 400,000 women)
  4. How many are likely to have a university degree?
    (26% -> 104,000 women)
  5. How many are likely to be attractive?
    (5% -> 5,200 women)
  6. How many are likely to find me attractive?
    (5% -> 260 women)
  7. How many am I likely to get along well with?
    (10% -> 26 women)

Leaving him with just twenty-six women in the whole world he would be willing to date.

Just to put that into perspective, that means there are around four hundred times more intelligent civilizations living on other planets than potential partners for Peter Backus.

Personally, I think that Backus is being a little picky. In effect, he’s suggesting that he only gets on with one in every ten women he meets, and that he only finds one in twenty attractive enough to go out with. This means he’ll have to meet up to 200 women to find one that fits just these two criteria. And that’s not even taking into account whether she likes him.

I think there’s room to be a bit more generous. Maybe the numbers should go a little more like this:

How many people of the right gender are there who live near me?
(In London -> 4 million)

How many are likely to be of the right age range?
(20% -> 800,000 women)

How many are likely to be single?
(50% -> 400,000 women)

How many are likely to have a university degree?
(26% -> 104,000 women)

How many are likely to be attractive?
(20% -> 20,800 women)

How many are likely to find me attractive?
(20% -> 4,160 women)

How many am I likely to get along well with?
(20% -> 832 women)

Almost a thousand potential partners across a city, then. Seems much more like it, in my book.

But there is another issue.

If Backus could relax some of his criteria just a bit, he’d have a much bigger pool of potential partners to work with. In fact, he could instantly quadruple his chances if he were a little less fussy about his future love holding a university degree. And the pool of ladies would be much, much larger if he were willing to expand his search to outside of London.

Strangely though, opening our minds to all potential partners seems to be the opposite of what we do when we’re single. I recently heard of a gentleman with an even clearer idea of what he was looking for in a potential partner. This man had set up a profile on the dating website OkCupid, which offers a profile section where you can outline certain “deal-breakers”: things that you can’t tolerate under any circumstances. His list ran to over a hundred, and was so extreme that it became the subject of a popular article on the website BuzzFeed. Under the heading “Do Not Message Me If” were the following gems.

1. You needlessly kill spiders

2. You have tattoos you can’t see without a mirror

3. You discuss Facebook in the visceral world

4. You consider yourself a happy person

5. You think world peace is actually a goal of some sort

As reasonable as it is to limit your search to a spider-loving, ink-free peace hater, unfortunately, the more deal-breakers you have the less likely you are to find love.

Because when you feed a mammoth list like this one into Backus’ equation — or even my version — unfortunately, you’ll get an answer close to zero potential partners. Of course, we all have must-haves and no-nos when it comes to love. But an extensive list like this does raise an interesting question. Just how much do our preemptive dating criteria actually harm our chances of finding love?

The reality is that when people are single and looking for a prospective partner, they often add in all sorts of must-haves or must-not-haves that dramatically reduce their chances. I have a very close friend who ended a potentially fruitful courtship simply because the gentleman wore black shoes with blue jeans to a date. I have another chum who insists that he cannot date a woman who uses exclamation marks! (That one is for him.) And how many friends do we all know who will not consider someone unless they are driven enough, or gorgeous enough, or rich enough?

Being good on paper doesn’t mean anything in the long run. There’s no point in restricting your search to people who match everything on your checklist, because you’re just setting yourself an impossible challenge. Instead, pick a couple of things that are really important and then give people a chance. You might just be pleasantly surprised. Let’s be honest, we probably all know people who’ve ended up with someone they never thought they’d be with, even if that person were the last life-form on the planet. After all, in the words of Auntie Mame, “Life’s a banquet, and most poor suckers are starving to death!”

Just ask Peter Backus. He beat his own odds; he got married last year.

Excerpted from Hannah Fry’s TED Book, The Mathematics of Love, which also offers witty and useful analyses of other pressing romantic questions like: How do you choose a wingman? When should you settle down? How should you plan the seating at your wedding? And, of course, how to live happily ever after.

Hannah’s TED Book, The Mathematics of Love, is available now at booksellers worldwide. Watch her TED Talk on

Illustrations by Christine Rösch



A home for books and authors on Medium

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store
TED Talks

TED Talks

The official feed for Ideas worth spreading.