What if I tell you that you can accurately guess someone’s birthday just by having them follow a series of steps?
Can you imagine how much of an impact this would create?
Imagine meeting a person for the first time — or having them come up on stage as a subject.
Have them tell you about their favorite birthday memory.
Then deepen your connection by telling them the way they shared their memory shows you how important this day is to them, and afterward, guess what month and day they were born.
Wouldn’t it be astounding if you could do this precisely? Any month. Any date. Any person.
And you don’t even have to ask a single question.
Today, we’re going to teach you the mentalism guess birthday – how it’s done without asking.
Let’s begin!
How to Do the Mentalism Guess Birthday
For this trick, you’ll be using the mental math method.
Before anything else, the calculations to this trick may become complicated, so make it easy for your subject by giving them a calculator. Or, if you want to build their trust, have them use one of their phones — this way, no one can say that you rigged the device.
Also, make sure you lay down the rules. Remind your subject that after each step, they need to press the equal sign. That’s the only thing they need to remember.
You, on the other hand, need to remember a whole lot more! Make sure you’re on the same page — once you get confirmation, you can begin.
Step 1: The Birth Month
Start by having them find the corresponding number to their birth month. January = 1, February = 2, March = 3, so on and so forth. Have them enter the number in the calculator.
Let’s say your subject’s birthday is in May. So she’ll press 5.
Then, have her multiply it by 7. Make sure she presses the equals sign afterward.
5 x 7 = 35.
Have her subtract one from her current number.
35 – 1 = 34.
Here’s where your subject will appreciate the calculator. Have her multiply the number on the screen by 13.
34 x 13 = 442.
Step 2: The Birth Date
Have her add her birth date to the current number.
Let’s say she was born on the 27th, so 442 + 27 = 469.
Now, have her add 3 to her current number.
469 + 3 = 472.
We’ll increase the number significantly again. Whatever number your subject has on the screen, multiply it by 11.
472 x 11 = 5,192.
The next step is to have her take away two numbers. First, have her subtract her birth month, press the equal sign, then subtract her birth date.
5192 – 5 (birth month) = 5,187.
5187 – 27 (birth date) = 5,160.
Divide the current number by 10.
5,160 / 10 = 516.
Finally, tell her to add 11 to her current number.
516 + 11 = 527.
Have her read out the number.
The last two digits will always be the birth date. The remaining numbers represent her birth month. In this case, since she ends up with 527, it means she was born on May 27th.
Pretty amazing right?
Pro Tips to Spice Up Your Mentalism Guess Birthday Performance
As with all tricks, the more you do it, the more ways you find to enhance it. The changes don’t have to be drastic. In fact, at its core, the trick remains the same.
But there’s more than just the steps that make a performance incredible. Putting tweaks here and there can up the ante of your act and bring it to a higher level.
Here are a couple of things you can try.
Tip #1: Combine It with a Bit of Mind-Reading
The instant your subject presses the equals sign after adding the final number, they’ll see how the numbers on the screen show their birthday. They will know all they need to do is show you the screen, and it’s a matter of interpreting the numbers of the screen.
But what if you never have to see the screen at the end? Wouldn’t that be more impressive?
A less obvious way to go about the trick is to stop after you’ve asked to subtract the birth month and birth date. Have them give you the number on the screen before you continue.
Although it may look like you’re getting help, the connection to her birthday is barely there. You can do the last two steps in your head. The best thing about it is that it’s relatively simple math.
The step after that is to divide it by 10 — all you need to do is drop the last digit. Then add 11, and you’ll end up with the numbers that allow you to guess her birthday.
The last two steps are the same, but doing it in your head adds a layer of complexity that will amaze your subject and the audience.
Tip #2: Use Props If You’re Bad at Math
Doing the last two steps in your head is impressive, but if you’re bad at math, it might be a recipe for disaster.
Imagine the stress of having to do the mental calculations silently in your head under pressure. Also, you can’t let go of your persona, so you have to keep the conversation going.
Don’t panic!
No mentalism rule says you can’t reveal your subject’s birthday by writing it down on a piece of paper.
It buys you a bit more time, which takes off a bit of the pressure, especially if you’re terrible at math.
You can also use your marker to help you with the computations (sometimes math is more manageable when you have visual cues).
The best part is as long as you keep your writing tiny, you can always scribble something over it and build it into your trick!
Tip #3: Pretend to play it by ear
Typically, when mentalists do mental math tricks, they purposely give subjects instructions one after the other. For tricks like The Grey Elephant in Denmark or the Red Hammer, you don’t want them having more time because they might think of something else.
With this trick, you don’t have to follow such a rapid pace.
You can build the drama by giving the impression that you’re choosing the next step as you go along.
You can even throw in a couple of false starts. You can say something like, “Let’s add a tweeel — no, no, that’s not right. An eleven! That feels right. Let’s add an eleven to what you have now.”
The difficulty with this route is you have to practice your patter. It’ll stretch your performance, so if you don’t know the steps like the back of your hand, you might end up confusing yourself.
Wrapping Things Up
No matter what their birthday is, you can’t go wrong as long as you follow these steps. But like any other mentalist trick, it’s easier said than done.
Reading through the instructions is one thing. Putting it into practice is something completely different.
So take the time to try it out. Find your rhythm when you’re doing the trick. Put in your patter.
The tips are there as enhancements — they don’t make or break your performance. You do.
And as long as you put in the work, you’ll do great.