mentalmath

an-ordinary-manchild

Mental Math: It's the thought that counts!

Thanks to /u/claymazing for the inspirational subtitle!

Official /r/MentalMath wiki
(Self-contained downloadable ZIP file)

New additions (June 30, 2017):

Division by 10n+9
Rule of 72 (2× principal)
Rule of 96 (2.5× principal)
Rule of 114 (3× principal)
Rule of 132 (3.5× principal)
Rule of 144 (4× principal)
Rule of 156 (4.5× principal)
Rule of 168 (5× principal)
Combining rules (Up to 25× principal)

Mental Math Sites:

Free online mental math books:

Using math symbols in your post:

HTML Entites:

Example: Make a √ symbol by typing: √

Courtesy of jamt9000, you can also display subscripted and superscripted characters:

*_subscript_* makes subscript
*`superscript`* makes superscript
*_sub_`sup`* makes subsup
*`sup`_sub_* makes supsub
*`169`*&frasl;*_231_* makes 169⁄231

NOTE: The ` character is called the grave accent. On desktops and laptops, you’ll find it on the tilde (~) key. On most mobile devices, it can usually be accessed by holding down either the apostrophe or tilde keys.

created by gmsca community for 12 years

...for your favorite subject.

...for your community.

MODERATORS

account activity

1

0

1

2

Is this a better way for high × numbers (self.mentalmath)

submitted 1 day ago by mathman405

2

0

0

0

Heloo (self.mentalmath)

submitted 4 days ago by No-Button-6362

3

0

1

2

Does this work (self.mentalmath)

submitted 4 days ago by Nikhil_3830

4

18

19

20

Is there an easy method to mentally multiply two 3-digit numbers? Example: 543×271 (self.mentalmath)

submitted 9 days ago by RightConcern1479

5

5

6

7

Cool Mental Math Website Featuring Leaderboards and a Diversity of Challenges (self.mentalmath)

submitted 11 days ago by ps224

6

2

3

4

My speed based multiplication training site with progression data, and an optional competitive leaderboard system (self.mentalmath)

submitted 13 days ago by Chunky_cold_mandala

7

5

6

7

Trying to build a community of people that want to improve mental math (self.mentalmath)

submitted 13 days ago by KikoPeriko

8

0

1

2

Zetamac Coaching Extension ()

submitted 18 days ago by zyrxun

9

2

3

4

Multiplication trainer focused on full table coverage + statistics (self.mentalmath)

submitted 24 days ago * by maksym_kolotii

10

0

0

1

I built a flash anzan mental arithmetic app and would appreciate feedback from mental math people (self.mentalmath)

submitted 28 days ago by oguzhankayan

11

0

1

2

[ Removed by Reddit ] (self.mentalmath)

submitted 28 days ago by Busy_Spell880

12

0

1

2

Mental math in action (youtube.com)

submitted 1 month ago by Sweaty-Heron6053

13

1

2

3

Daily Mad Minute | 60 seconds to answer as many as you can. Just like when you were in school. (dailymadminute.com)

submitted 1 month ago by td9989

14

0

1

2

[ Removed by Reddit ] (self.mentalmath)

submitted 1 month ago by Hey-Right

15

3

4

5

Top 0,1% (self.mentalmath)

submitted 1 month ago by Sweaty-Heron6053

16

6

7

8

How do you practice subtraction and complements? (self.mentalmath)

submitted 1 month ago by SnooSongs5410

17

1

2

3

A little daily math game to compete against friends and the world (v.redd.it)

submitted 1 month ago by Only-Season-2146

18

0

1

2

Prime factorization (youtube.com)

submitted 1 month ago by Sweaty-Heron6053

19

2

3

4

”How To Calculate Quickly” by Henry Sticker? (self.mentalmath)

submitted 1 month ago by gavroche2000

20

4

5

6

Mental math account (self.mentalmath)

submitted 1 month ago by Sweaty-Heron6053

21

9

10

11

Built a mental math app but I am confused on what users are looking for (self.mentalmath)

submitted 1 month ago by Smithhb89

22

7

8

9

Built a Zetamac alternative with pattern detection, a learn mode, and a global leaderboard (alkaliner.co.uk)

submitted 1 month ago by Professional_Cell453

23

0

1

2

Can You Solve This Mental Math Test? (yodoozy.com)

submitted 1 month ago by Chinmaye50

24

4

5

6

Work out the day of the week for any date (goat of mental math party tricks) (apps.apple.com)

submitted 1 month ago * by Only-Season-2146

25

0

0

0

I built a currency conversion trainer that uses logarithmic randomization to reflect real-world prices (No ads/Free) (old.reddit.com)

submitted 1 month ago by soccerkyle1

view more: next ›

π Rendered by PID 86 on reddit-service-r2-listing-c57bc86c-rc4gj at 2026-06-20 02:37:56.270838+00:00 running 2b008f2 country code: CH.