r/mentalmath

2.2K archived posts · Mar 2014 – Sep 2026

MentalMath: It's the thought that counts

r/mentalmath

Want to learn how to do math in your head, or even just wrap your head around a mathematical concept? This is the place!

Created Mar 24, 2014

4.7KMembers (last snapshot)

2.2KArchived posts

Mental Math: It's the thought that counts!

Thanks to u/claymazing for the inspirational subtitle!

[Official r/MentalMath wiki](https://www.dropbox.com/s/dj4gw77gipj3b08/mentalmathwiki.zip?dl=0)
(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:

BEATCALC
BetterExplained.com
r/CasualMath
CuriousMath (Archived)
Flying Colours Maths
r/funmath
Grey Matters
Intuitive Calculus
Math Dude
Math-Magic.com (Archived)
Math Memoirs
Math StackExchange
Math Tricks For Kids
Math Vault
Mental Math Guide
MindMagician.org
Numberphile
Plus Maths
Quickermaths
The Math Behind The Magic

Free online mental math books:

101 Shortcuts in Math Anyone Can Do by Gordon Rockmaker
Cracking the Mental Math Code: A Repertoire of Number Sense Techniques by Yash Chandak
General Method for Extracting Roots using (Folded) Continued Fractions by Manny Sardina
High Speed Math by Lester Meyers
How to Become a Lightning Calculator by John Regan
Inner Algebra: How To Do Algebra In Your Head by Aaron Maxwell
Integrate Your Brain: How To Do Calculus In Your Head by Aaron Maxwell
Math and Memory Short Cuts
Mathematician's Delight by W.W. Sawyer
Manu-Mental Computation by Woodford Dulaney Anderson
Nix The Trix by Tina Cardone
Number Sense Shortcuts for Beginners by Larry White
Number Sense Tricks by Bryant Heath (Dropbox Mirror)
The Power of Vedic Maths by Atul Gupta
Practical Short Methods in Rapid Calculation by William Bell
Quick And Easy Math by Isaac Asimov
Rapid Calculations by A. H. Russell
Secrets of the Calculation Artist by Philipp Maennchen
Short-Cut Math by Gerard W. Kelly
The Speed Math Bible by Yamada Takumi

Using math symbols in your post:

HTML Entites:

Example: Make a √ symbol by typing: √

Mathematical symbols
Fractions
Greek letters
Subscripted and superscripted characters

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`*⁄*_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.

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