web metrics

Lightning Calculation CalendarI have researched and written about methods of mental calculation over the years, and I’m often surprised at the ingenuity evident in the mathematical methods developed specifically for it. Based on my Lightning Calculator series of essays here, I’ve created a new 2011 calendar titled Lightning Calculation. It’s a unique, interactive calendar for developing abilities in mental calculation. You can download a free PDF file for printing on your computer, or if you prefer, order it for delivery through Lulu.com. I also think it might be a nice thing to make as a Christmas gift for someone interested in this sort of thing, or for displaying in a math classroom.

NOTE:  If you choose to have the calendar professionally printed by Lulu.com rather than on your own printer, through December 31 you can enter the code REMARKABLEYEAR305 at checkout for 20% off the price of $17.60. The Lulu site is also posting daily coupon codes in December here.

A different field of mental calculation is treated each month in this calendar, from 2-digit multiplication to square roots to factoring to logarithms and more. The upper half of each calendar page describes methods that can be used to solve problems of that month, and the lower half offers opportunities to test yourself and practice these techniques daily using the actual dates shown in the calendar. Of course, you should feel free to try all the dates at once, or bounce around between months, or do whatever you want. After all, this is all for fun!

Every month includes a legend that describes how the dates are used in the calculations. In nearly all cases the answers are provided right in the calendar itself, printed in number boxes connecting the dates involved in the calculation but small enough that they are not visible from a distance. Every day starting in February also poses a day-date calculation. In all, there are nearly 4000 exercises in mental calculation embedded in this calendar!

The calendar is  available for downloading and printing at the link below. The format is two-sided 8-1/2″ x 11″ sheets of paper printed in landscape mode that can be connected at their edge. This could be printed to fit on A4 or other sizes, I’m sure. I recommend printing it on colored paper; although it looks fine on white paper, the color scheme is really designed for a light beige or ivory paper and it looks so much more professional when it’s printed on paper of some color. In the past I’ve had a local office shop (Kinko’s FedEx) add clear plastic sheets to the front and back and install a spiral wire (a 60-second job that costs $5). Drilling a hole in the center along the top to hang it completes the calendar. Using 3 rings through punched holes along the top may be a cheaper option.

Alternatively, and in response to comments on last year’s calendar, it is available for ordering from Lulu.com if you prefer. The downloadable PDF file below has all the resolution of the Lulu.com version—the only difference between them is that the Lulu version has a light beige/ivory background that I did not include in the downloaded PDF to save printer ink. The photo above is of the Lulu.com version, which is beautifully printed. The calendar is listed on the site as a coil-bound book that you turn sideways to use (it’s not in the calendar category), and you will have to punch or drill a hole in it to hang it on a hanger.

Small images of the front and back and each page of the calendar are shown below. These provide only a rough idea of the content, but if you think you might be interested, the complete PDF file is just over 10MB, so it is easily downloaded and viewed at full resolution. The last page is flipped upside down in order that the back of the calendar has the same orientation as the front cover.

The PDF of the calendar for personal printing is found here.

The calendar on Lulu.com is found here.

Hope you like it.  Have a happy 2011!


Front and BackIntroduction Pages 1


Introduction Pages 2 January


February March


April May


June July


August September


October November



[Please visit the new home for Dead Reckonings: http://www.deadreckonings.com]

25 Responses to “A 2011 “Lightning Calculation” Calendar”
  1. Lisa PT says:

    Absolutely amazing. I just ordered it. This is my family’s calendar for the next year.

    Thanks! — Ron

  2. Anne says:

    Awesome work!

    Thanks, Anne. I appreciate your nice comment. — Ron

  3. Bill Bourn says:

    Nice Work. Ever hear of Trachtenberg’s methods? I may have spelled the name wrong but I think he had a complete arithmetic system. Look at wikipedia.

    Hi Bill. I read the Trachtenberg book many years ago.There are some similarities but it is a little different. My impression is that it’s more designed for faster written calculations than for faster mental calculations. — Ron

  4. Free downloadable Mentat training calendar for 2011 - machine quotidienne says:

    […] appeared on my radar at the end of the year. Well, I’ve been keeping an eye peeled, and Ron just released his 2011 calendar. It’s not about graphical computing, but what is perhaps an equally interesting mathematical […]

  5. Luke says:

    Very nice. Always glad to see someone add (positively) to human performance. TAKE THAT REALITY TV!

    That’s the great thing, of course, about the Internet. I’m constantly inspired by what others create online and the interactions I have with people who contact me about my little blog. — Ron

  6. David Rysdam says:

    Already ordered one to go with my 2011 Theoni Pappas “math a day” calendar. Good way to wake up every morning.

  7. ChrisC says:

    Perfect!!!!, greetings from Colombia

  8. Markus says:

    $3.99 for a great geek calendar? Nice!

    That was a great Lulu discount! Since it expired on Nov. 30, I’ve been trying to keep tabs on new coupon codes and list them at the top of this post. — Ron

  9. Jagger says:

    Simply stunning presentation equally worthy of the mathematical principles of mental calculations…. and it has my birth date called out in one of the example giving a nice touch of personalization. Nice Job!

  10. James says:

    I find it hard to believe that after the great many mistakes in the Dead Reckonings book that there would be more mistakes in this calendar. please tell me that the .pdf file I downloaded has been fixed before the printing of the actual calendar.

    Square root of 5163: N  51.63, A = 7, R0 = 51 – 72 = 2 Estimate: 7 R0=2

    Should say 51-49=2 and NOT 51-72

    Ah, you’re right. The 72 should have been 7^2 but the exponent was dropped in the process of copying and pasting, and there are three instances in that particular box where I missed restoring them. I have updated the downloadable PDF file and the Lulu version of the calendar. This also happened in the upper left box of February in the very initial version. Hopefully the text description above the examples, which is correct, helps to identify these. Those with earlier versions might want to download the new version or pencil in the changes. Thanks. — Ron

  11. James says:

    Here is another mistake

    log 49 = log 72 = 2 log 7

  12. Lightning Calculation Calendar « Engineer & Entertain says:

    […] gentleman who created the 2010 nomogram calendar has created a calendar for 2011 which will add in your ability to do lightning calculations.  If you have ever wanted to convince […]

  13. DIY Kalender 2011 | D I Y says:

    […] ist natürlich das Make Magazine) sind wir auf einen ganz phantastischen Kalender gestossen: Der “Lightning Calculation”-Calendar widmet sich nicht etwa Risikokalkulationen im Bezug auf anstehende Donnerwetter, sondern Techniken […]

  14. DanA says:

    Great job, Ron. Many thanks!

    Another minor correction. In the list of historical dates, February 1, 2003, corresponds to the *Columbia* space shuttle disaster. The Challenger disaster happened on January 28, 1986.

    Ah, thank you very much, DanA. I will make this update to the downloaded version and the Lulu.com version this weekend when I’m back in town. — Ron

  15. Walking Randomly » Carnival of Mathematics #73 – Chuck Norris Edition says:

    […] up we have a mathematical calendar for 2011 courtesy of Ron Doerfler which focuses on Lightning Calculations.  I have written about […]

  16. Another beautiful, interesting calendar from Ron Doerfler — The Endeavour says:

    […] has made a new calendar and this year’s theme is lightning computing, tricks for mental calculation. The calendar is available for download as a PDF or for purchase in […]

  17. sarah says:

    I just wanted to let you know that I find your blog fascinating and I included the link in my weekend links round-up. I’m a food blogger, but maths teacher is my full time job, so I often include a maths link in my round-ups. I’m enlarging the reading habits of my followers. :)

    Thanks, Sarah! A rare mix of interests, but I imagine your blog on recipes is a nice break after a day of teaching math. I’ve posted fewer essays this year (not due to indifference, but rather the opposite problem of being incredibly busy with nomograms and other fun stuff), but I’ll have more posts this year. The food on your site looks delicious, so here’s a way to enlarge the reading habits of my readers as well. — Ron

  18. Wild About Math bloggers 1/28/11 » Fun Math Blog says:

    […] telling us about an amazing lightning computing calendar produced by Ron D and available at the Dead Reckonings blog. It’s free as a PDF download or you can buy a printed copy at […]

  19. Nifty Interactive Math Calendar Makes Unique Gift | SpottyBanana says:

    […] author of the Dead Reckonings Blog, has created an awesome free 2011 mental math calendar called Lightning Calculation. Ron describes this calendar as an interactive calendar for developing abilities in mental […]

  20. eviltoad says:


    Shame I missed it for this year. Will there be a 2012 edition?

    Thanks for asking! I may resurrect it for 2012, as I haven’t had time to create a new calendar for next year. I’ll see, and if I do I’ll email you and let you know. — Ron

  21. Eric G. says:

    I second interest in a 2012 version. I’d love to have one

  22. BitterTait says:

    Thirded 2012. I’d buy at least 2, one for home and one for the cubicle.

  23. eviltoad says:

    Thanks Ron

  24. Steven says:

    Another vote for a 2012 calendar!!

  25. Freddie Hand says:

    Can you try to use the division method on the square root method given on the dead reckoning online material?