20 Number Magic Tricks: Read Minds with Math!

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Perform math magic to ace your arithmetic + amaze your friends

Co-authored by David Martinez and Sophie Burkholder, BA

Last Updated: October 26, 2024 Fact Checked

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Magic Mind Tricks with Numbers

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Mental Calculations

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Tricks with Paper or Dice

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Expert Interview

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Expert Q&A

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Amaze your friends, relatives, and teachers with these number-based mind tricks! Whether you want to be able to do math quickly in your head or blow your friend’s mind with some numerical hocus-pocus, we have the ultimate list of mind tricks for you to master. Plus, we’ve included some extra number magic tricks if you just so happen to conjure up a piece of paper or set of dice. You’ll be a mind-reading math whiz in no time!

Magic Tricks with Numbers

Think of a number between 1 and 10. Then, add 2, multiply by 2, subtract 2, divide by 2, and subtract the original number from the quotient. The answer will always be 1.
Think of any number and multiply it by 3. Then, add 6, divide by 3, and subtract the original number from the most recent result. The answer will always be 2.
Think of any number. Then, double the number, add 9, subtract 3, and divide by 2. Subtract the original number from this result. The answer will always be 3.

Section 1 of 3:

Magic Mind Tricks with Numbers

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1
Trick #1: Think of a number between 1 and 10 Choose a number between 1 and 10. Add 2 to your number, then multiply that result by 2. Subtract 2 from this product, then divide by 2. Subtract the original number from your most recent answer to get the final result.^{[1]
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- The final result will always be 1.
- For example, say the original number is 5. 5 + 2 = 7 → 7 x 2 = 14 → 14 - 2 = 12 → 12 ÷ 2 = 6 → 6 - 5 = 1.
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Trick #2: Think of any number and multiply it by 3 Choose a number and multiply it by 3. Add 6 to this product, then divide the new result by 3. Subtract the original number from the most recent calculation to get your final result.
- The final result will always be 2.
- For example, say the original number is 8. 8 x 3 = 24 → 24 + 6 = 30 → 30 ÷ 3 = 10 → 10 - 8 = 2
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Trick #3: Think of a number between 1 and 20 Choose a number between 1 and 20. Add 1 to the number, then double the new sum. Add 4 to this number and then divide it by 2. Subtract the original number for the final result.
- The final result will always be 3
- For example, say the original number is 4. 4 + 1 = 5 → 5 x 2 = 10 → 10 + 4 = 14 → 14 ÷ 2 = 7 → 7 - 4 = 3.
- Another variation on this trick is to think of any number, then double that number, add 9, subtract 3, and divide by 2. Subtract the original number from your most recent result to get 3.
4
Trick #4: Think of any number and add it to the next-highest integer Select any number, then think about the next-highest number. Add those two neighboring integers together. Then, add 9 to this sum, then divide the result by 2. Finally, subtract the original number to get your final result.^{[2]
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- The final result will always be 5.
- For example, let’s say that the original number was 10. The next highest number is 11, so 10 + 11 = 21 → 21 + 9 = 30 → 30 ÷ 2 = 15 → 15 - 10 = 5.
5
Trick #5: Think of any number between 20 and 100 Pick a number between 20 and 100 and add each digit of this number together to get a single sum. Then, subtract that sum from the original number to get the difference. Finally, add each digit of the difference together for your final result.
- The final result will always be 9.
- For example, let’s say that the original number was 64. 6 + 4 = 10 → 64 - 10 = 54 → 5 + 4 = 9.
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Trick #6: Think of any number and add 5 to it Choose a number and add 5. Multiply this sum by 3. Then, subtract 15, divide by the original number, and add 7 to get the final result.
- The final result will always be 10 .
- For example, let’s say that the original number was 20. 20 + 5 = 25 → 25 x 3 = 75 → 75 - 15 = 60 → 60 ÷ 20 = 3 → 3 + 7 = 10.
7
Trick #7: Think of a 3-digit number that has 3 different digits Pick a 3-digit number with three unique digits; for example, you could choose 583 or 204 but not 224, 919, or 555. Reverse the digits to get a new number, then subtract the smaller number from the larger one. Add up the digits of this new result to get the final answer.^{[3]
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- The final result will always be 18.
- For example, let’s say that the original number was 291. When reversed, 291 becomes 192. 291 - 192 = 99 → 9 + 9 = 18.
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Trick #8: Think of a 3-digit number where every digit is different Choose a 3-digit number with three different digits; for example, you could choose 201 or 948 but not 333, 818, or 400. Reverse the digits so that you have a new three-digit number. Subtract the smaller number from the larger number to get another 3-digit number, then reverse the digits of the difference and add this reversed number to the original difference.^{[4]
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- The final result will always be 1089.
- For example, let’s say the original number was 845. When reversed, 845 becomes 548.
- 845 - 548 = 297 → 792 + 297 = 1089.
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Trick #9: Think of a number between 1 and 8 Choose a number between 1 and 8 and multiply that number by 2. Multiply this product again by 5. Subtract 5 from the most recent result, then add 7 to get your final answer.
- The first digit of the answer will be your original number, and the second digit will be 2.
- For example, let’s say the original number is 7. 7 x 2 = 14 → 14 x 5 = 70 → 70 - 5 = 65 → 65 + 7 = 72.
- In the number 72, 7 was your original number, and the second digit is 2.
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Trick #10: Think of a number between 1 and 6 Select a number between 1 and 6 and multiply that number by 9. Take that result and multiply it by 111, and then multiply that result by 1001. Finally, divide your most recent result by 7 to get the final answer.
- The final answer will always contain some combination of the numbers 1, 2, 4, 5, 7, and 8.
- For example, let’s say the original number is 3.
- 3 x 9 = 27 → 27 x 111 = 2997 → 2997 x 1001 = 2,999,997 → 2,999,997 ÷ 7 = 428,571.
- You may need a calculator to do the division and multiplication of these large numbers.
11
Trick #11: Think of any even number and multiply it by 6 Choose any even number and multiply it by 6. The last digit of your result will end with the same digit as your original number. The digit in the ten’s place of the original number will be half of the digit in the one’s place.
- For example, let’s say that the original number is 12 (but you didn’t know that). The final result will be 72 (12 x 6 = 72).
- Working backwards, you know that the last digit of the original number is 2. That gives you a final result of _2.
- You also know that the original number’s ten’s place digit will be half of its one’s place digit. Because you now know that the digit in its one’s place is two, then the digit in the ten’s place must be 1.
- You now have the original number: 12.
12
Trick #12: Think of a 3-digit number that repeats the same digit Come up with a 3-digit number that’s made up of the same repeated digits (e.g., 333, 444, 555). Add each digit together and find their sum. Divide the original number by the sum of its digits to get the final result.^{[5]
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- The final result will always be 37.
- For example, say the original number was 222. 2 + 2 + 2 = 6 → 222 ÷ 6 = 37.
- You may need a calculator or piece of paper and pencil to complete the long division in this trick.
13
Trick #13: Think of a 6-digit number with two repeating 3-digit numbers Choose a six-digit number that’s composed of two repeating three-digit numbers (e.g., 291,291, 483,483, 102,102). Divide the number by 7, then again by 11, and a third time by 13. The final answer will be the three-digit number that’s repeated in the original six-digit number.
- For example, let’s say the starting number is 146,146. 146,146 ÷ 7 = 20,878 → 20,878 ÷ 11 = 1,898 → 1,898 ÷ 13 = 146
- You may need a calculator or piece of paper and pencil to do the long division in this trick.
14
Trick #14: Multiply the first digit in your age by 5 Add 4 to your answer, then double this most recent sum. To this doubled number, add the second digit of your age. Subtract 8 from this number to get your real age.^{[6]
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- For example, say that you are 32 years old. 3 x 5 = 15 → 15 + 4 = 19 → 19 x 2 = 38 → 38 + 2 = 40 → 40 - 8 = 32.
- Note that this trick only works if you’re between 10 and 99 years of age.
- A variation on this trick asks you to follow these steps instead: double your age, add 2, multiply by 5, and subtract 10. This calculation will give you your age with a zero added at the end.
Impress friends at a party. "I was looking for a way to break the ice at a small get-together. This simple number prediction trick was a big hit! I had everyone amazed that I could read their minds. It sparked fun conversations trying to guess how it worked." - Syeda S.

Bond with grandkids over math magic. "My grandkids visit every summer and I'm always looking for new activities. The age guessing trick was perfect for making math entertaining. They begged me to teach them after I guessed their ages exactly right." - Phoebe M.

Liven up math lessons with tricks. "As a 5th grade teacher, I'm always trying to make math exciting. These number tricks have been a great way to engage my students. They get a kick out of trying to stump each other with different variations. Their math skills improve while having fun!" - Susan H.

Impress a date with mentalist abilities. "I wanted to surprise my date with something unique on our next outing. This article gave me some great math-based tricks to try out. When I guessed her age exactly, she was extremely impressed! It led to a fun conversation about math and magic." - Jithin K.

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Section 2 of 3:

Mental Number Calculation Tricks

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1
Multiplying any two-digit number by 11 in your head Visualize the two-digit number you want to multiply by 11. Separate the two digits in your mind. Add the two digits togethers to get a sum.^{[7]
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Research source} If the sum is equal to or lesser than 9, place the sum in between the two digits to get your final result.
- If the sum is greater than 9, put the sum’s one’s digit in the space and carry the ten’s digit to be added to the first digit in your original number. Now you have your final result.
- For example, let’s say the original number is 72. 7 + 2 = 9 → 7 9 2 → 792 = 72 x 11.
- In another example, let’s say the original number is 57. 5 + 7 = 12 → 5 12 7.
- Because 12 is greater than 9, you must put the 2 in the space between the digits then add together 1 and 5. Your final result will be 627 = 57 x 11.
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Multiplying by 9 with your fingers Place both hands in front of you with all fingers extended. To multiply 9 by a given number, count from the left and fold down the finger that corresponds with that number (e.g., your left pinky would be 1 and your right ring finger would be 9). Count the fingers on either side of the folded finger to get your result.^{[8]
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- For example, say you want to multiply 9 by 5. Fold down the fifth finger from the left—your left thumb.
- You now have four fingers to the left of your folded thumb, and five fingers to the right. The answer is 45.
3
Dividing large numbers in your head If you want to divide a large number and would normally have to use a calculator, try these handy division tricks instead! These divisibility shortcuts may help you do the math more easily in your head:^{[9]
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- A number is divisible by 2 if the last digit is a multiple of 2 (e.g., 210).
- A number is divisible by 3 if the sum of the digits is divisible by 3 (e.g., 522).
- A number is divisible by 4 if the last two digits are divisible by 4 (e.g., 2540).
- A number is divisible by 5 if the last digit is 0 or 5 (e.g., 9905).
- A number is divisible by 6 if it passes the rules for both 2 and 3 (e.g., 408).
- A number is divisible by 9 if the sum of the digits is divisible by 9 (e.g., 6390).
- A number is divisible by 10 if the number ends in a 0 (e.g., 8910).
- A number is divisible by 12 if it passes the rules for both 3 and 4 (e.g., 180).
- For example, if you’re trying to divide 210 books into equal groups, the books can be evenly distributed into groups of 2, 3, 6, and 10.
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Memorizing the first seven digits of pi To memorize the first seven digits of pi, all you need to do is memorize the sentence “How I wish I could calculate pi.” Count the number of letters in each word of the sentence and place them in order to get the first seven digits of pi, which are 3.141592.
- “How” has 3 letters, “I” has 1, “wish” has 4, “I” has 1, “could” has 5, “calculate” has 9, and “pi” has 2.
- If you have a really great memory, try adding to this sentence to memorize more digits of pi!

Section 3 of 3:

Number Magic Tricks with Paper or Dice

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1
Paper Cards Trick Ahead of time, write the numbers 1-5 in the center of five blank pieces of paper. On each respective card, write the following digits around the center number: Card #1 (12611 & 1378), Card #2 (11910 & 12714), Card #3 (13910 & 11814), Card #4 (13912 & 1478), Card #5 (12611 & 141013). Lay your cards out on a table or flat surface before beginning your trick.^{[10]
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- Ask someone to think of a number between 1 and 14. Instruct them to point to the cards that their secret number appears on.
- Once they’ve pointed to their cards, look at the cards they’ve chosen and silently add together the center number in each one to get their secret number.
- For example, let’s say they chose the number 10. They would then point to card 2, 3, and 5—all of which feature the number 10.
- Adding together 2 + 3 + 5 gives you 10, revealing their secret number.
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Dice Trick Close your eyes and ask someone to roll two dice without telling you which numbers they land on. Ask them to multiply the number on the first die by 2, then add 5 and then multiply by 5. Then, tell them to add the number from the second die to this product and tell you their final result.
- In your head, subtract 25 from the final result. This will give you a two digit number—the first digit is the number of the first die, and the second digit is the number of the second die.
- For example, let’s say the person rolled a 4 and a 6.
- 4 x 2 = 8 → 8 + 5 = 13 → 13 x 5 = 65 → 65 + 6 = 71 → 71 - 25 = 46, giving you 4 (46) and 6 (46) as the two rolled numbers.

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Are there any other ways to perform the writing on a paper and prediction trick?

David Martinez
Professional Magician
David Martinez is a Magician based in San Jose, CA. David has over 20 years of experience and has performed throughout Northern California at weddings, private parties, team-building events, and more. He has notably performed for some of the biggest companies in the world, including Apple, Google, Facebook, and Uber. David previously served as President of the Silicon Valley Chapter of the International Brotherhood of Magicians and has received awards for Close-Up, Walk-Around, and Stage performances. In 2023, he co-authored Amaze and Delight: Secrets to Creating Magic in Business, aimed at helping individuals and organizations nurture healthy and happy business cultures.

David Martinez

Professional Magician

Expert Answer

So another intriguing method for performing the classic writing-on-paper prediction trick. Picture this: you've asked your participant to jot down something on a piece of paper, keeping it hidden from your view. They fold it, tear it, and perhaps even burn it to ashes. Then, as if by magic, you reveal the exact content of their thoughts. Here's the secret: while appearing to discard or destroy the paper, you actually retain a portion of it containing their written message. This sleight of hand is executed seamlessly while your audience's attention is diverted. For example, as you tear the paper or reach for a pen, you discreetly glance at the writing. This technique, known as "endurance" in the realm of magic, is a staple among mentalists. It allows you to obtain crucial information while maintaining the illusion of mystery and mind-reading prowess. By cleverly exploiting moments of distraction, you acquire the necessary insight to astonish your audience with seemingly supernatural abilities.

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What do you do if someone won't tell you the first digit of their age?

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Well, that means they don't want to play the game. If they refuse to play, just leave him or her alone.

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How does the third trick work?

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The third trick works because 111 divided by 3 is 37. So long as 111 and 3 are multiplied by the same multiple, the answer will always be 37. For example, if 111 (the dividend) is multiplied by 2, 3 (the divisor) should be multiplied by 2 as well in order to keep 37 as the quotient.

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If you know basic algebra, you can give yourself the extra challenge of puzzling out why these tricks work. For example, in the “Answer Is 3” trick, think of the person’s original number as x. You asked them to calculate $((x+1)*2)+4)/2)-x$ , which looks complicated but ends up simplifying to 3!

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Put a little showmanship and pizzazz into your mathematical magic act! Even if you already have the tricks and the final results memorized, pretend that you’re really concentrating on summoning the magic answer and reading someone’s mind with numbers.

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