A Sex Geek's Scientific Guide To What You Can Fit In Your Butt

Mind-blowing and helpful at the same time.

Scientific Guide To Knowing Which Size Anal Sex Toy To Try weheartit

My wife (sex educator Sunny Megatron) and I are geeks. We are actually proud geeks.

We don’t have sex, we have . . . SCIENCE!

I love science, Dungeons & Dragons, Star Trek, Star Wars, Dr. Who, math, history ... and sex. I’m a Sex Geek and my T-shirt from Reid Mihalko proudly proclaims that fact.

Of all the geeky sex facts I've encountered, this one is by far my favorite: If you haven’t had anal play in a while — let's say a month or longer — you can use the Fibonacci sequence of numbers to approximate the circumference of which sex toys (or other stuff) can now comfortably fit in your butt.


What!? Yes!

OK, I know this sounds confusing to most of you.

To those who understand this math, the thought of using the Fibonacci sequence to determine anal sizing is a bit unexpected, terrifying, and probably needs more explanation. Also, keep in mind, this is only used to go smaller, not larger in the size of anal dildos.

The Fibonacci sequence of numbers starts with 0 and 1. Then each subsequent number in the series adds the previous two whole numbers together: 0,1,1,2,3,5,8,13,21,34,55 and so on.

When graphed, this sequence of numbers creates the "Golden Spiral" which is reflected everywhere in nature.



You can see the Golden Spiral pattern in the shell of a mollusk, leaves on a stem, the shape of a galaxy and the uncurling of a fern. It's everywhere!

Everywhere includes your butt.

Now to say your butt is a golden spiral is not exactly correct, however, you can use the Fibonacci sequence to figure out mathematically what you can fit into your butt comfortably.


This is an especially useful tool if you haven’t had anal in a while.

As we relax and don’t use our anal sphincters for things other than defecation, the muscle shrinks up a bit because the muscle memory gets accustomed to what goes into or out of it. In other words, if you’re not putting a dildo in your ass, its sphincter gets smaller.

To figure out the size of what you can now put in your butt after an anal vacation, you will need two things: the circumference (in centimeters) of the last toy you put up your bottom and the Fibonacci sequence.

When you've figured out the circumference of the dildo, go back to the previous number in the Fibonacci sequence: THAT number is the new circumference of an object that will fit in your butt just fine!


Note: Remember to round up because we only deal in whole numbers in a Fibonacci sequence.

Let’s walk through a practical example!

1. Measure the circumference of the last toy used in your butt in centimeters.

Pat has a dildo that's about 1 ½ inches wide in diameter. That makes it equal to the around a 4.7 inch circumference, which rounds up to 5 inches (Circumference is determined by multiplying the diameter and multiplying it times Pi — 3.14).

We need to know what that number is in centimeters, so we multiply it times 2.54 to give us our number in centimeters. That makes the circumference 12.7 cm. 

2. Find the closest Fibonacci number to that measurement.


We round 12.7 cm up to 13 cm, which is a Fibonacci number.

3. Go back one number in the Fibonacci sequence.

The number before 13 in the Fibonacci sequence is 8. 


4. That number is the circumference in centimeters of what you can comfortably put in your butt.

For our example this would be 8 cm. Divide that number by 2.54 to convert back to inches, for a circumference of 3.2 inches. We then convert the circumference back to diameter by dividing it by Pi (3.14), for a measurement of around 1 inch in diameter as our answer.

5. Find any anal toy with a circumference small than that number that you like (remember to get one with a flared base!)

6. Have GREAT sex!

You're welcome.