You can read about my background as a test-prep tutor and developer by clicking here. For more information about the books mentioned on this page, click the links in the left-hand sidebar.

Please note: Total GMAT Math and Total GMAT Verbal were formerly known as The GMAT Math Bible and The GMAT Verbal Bible. For the sake of clarity, I've replaced the old names with the new names in the quotes below.

Total GMAT Math, Total GMAT Verbal, and other books

Now that students have been using my books to ace the GMAT for years, there are plenty of positive reviews and testimonials on sites other than this one. I've included some of those in addition to a sampling of the e-mails I get from happy customers.

Over at Beat the GMAT, user dkrich reports on how he got a 750:

I found Jeff Sackmann's blog, gmathacks.com to be very important to my preparation. I purchased his Total GMAT Math, printed it out, took it over to Kinko's, and had it bound. Then I worked through every chapter, and I revisited some several times because I just didn't have the concepts nailed down. I highly recommend making his materials an integral part of your preparation if you are rusty in math, and I assure you that I am receiving no monetary incentives for that endorsement!

Elizabeth got a 770!

I purchased two of Jeff's books: Total GMAT Math and The Official Guide to GMAT Review. I cannot stress enough how vital these books were to my study regimen. They are absolutely and completely responsible for how I performed on the test. Because the OG doesn't offer good explanations, doesn't rank each problem's difficulty, and doesn't have good math review, these books will fill in those gaps for you. I hadn't taken a math class since my freshman year of college 6 years ago, so Total GMAT Math saved me. I started each study session with one chapter from Total GMAT Math.

Ankur used Total GMAT Verbal to boost his Verbal score from 27 to 42!

First of all I must thank you profusely for the incredible insight provided by you in your Total GMAT Verbal. I must emphasize that without religiously following your advice, I would not have been able to achieve a score of 740(Q 49 / V 42).

Jeff has clearly been able to get into the psyche of the authors of GMAT and the tips are absolutely the best possible around, without exception. I think that the confidence in one's ability to beat the GMAT is a vital ingredient in achieving a good score and Total GMAT Verbal provides just that.

Finally, I must thank you once again for compiling the excellent book which is a fantastic tool for tackling the verbal portion of GMAT, more so for non-native speakers of english, like me.

Carrie hadn't done any math in more than two decades, but my books helped her get a 720!

I purchased the PDF books from GMAT Hacks (www.gmathacks.com) and these were great, especially for re-learning the math. The math book goes subject by subject through math teaching it. I did the books and all the questions in them.

Thomas bought all 1,800 of my practice questions, and it sounds like that decision worked out for him:

Thank you for the study materials for my GMAT Prep.

Got a 750 score for my recent test.

Bravo to you and your materials.

Here's Chad J's story (or click here for the full version).

I ordered Total GMAT Math and went through it religiously (pun intended). I went to work first through Total GMAT Math, then took that information and worked through the questions that I did in the Official Guide. As I worked through the guide I also had a look at the vast majority of your articles on the website. These were the only three references I used in my five-week study period.
I wrote the GMAT exam yesterday, 9 April, and received a grade of 760 (Quant: 48, Verbal: 47). I certainly didn't think that was possible a little over a month ago, and I largely attribute my success to the clear and concise explanations you provide in both Total GMAT Math and online articles. If anyone asks me for advice in preparation for the GMAT I will let them know that your book is a must-buy, and your website a must-bookmark.

At Beat the GMAT, Ram reports on his hard work, which paid off to the tune of a 680.

Total GMAT Math ... should be your bible for content knowledge development for the Quants section.

The Time for the remix blog reports on the best ways to prepare for the GMAT:

You need to go to www.gmathacks.com and buy damn near everything that Jeff Sackmann offers especially Total GMAT Math and any problem sets that you are having trouble with. They are well worth the money and will definitely help you.

Brandon found that Total GMAT Math made all the difference. You can read the full version of his post-test report here.

Having used virtually every study material available (OG, Princeton, Kaplan), Total GMAT Math is far and away the best study material available. Princeton Review's Math Review is junk in comparison. It was the best $50 I've ever spent.

My resources helped Luke reach a 760:

Just wanted to let you know, I took the GMAT yesterday and scored a 760 (Q49, V 45). I am stoked with that and I thought I'd let you know that your prep materials were the key to my quant score. I'm not a maths person - the verbal stuff came very easily but I needed a fair bit of work on quant. I used Kaplan Premier first, not bad for the basics, but then I used your Total GMAT Math and problem sets, and I wish I'd found them first. The result speaks for itself.

Kelly was able to reach her goal:

Had I known about your products before I started the gmat process, I would've saved myself a lot of time (and money!) - I had taken the gmat once before purchasing this, using only the manhattan gmat books as my guide. Your Total Math book was much more helpful in drilling (no pun intended) the concepts home. Just took the gmat again yesterday - I finished the quant section with time to spare and got to my goal of 700. I will definitely recommend your products going forward!

Olly also used many of my books, and he ended up happy with the result:

This is a note of thanks; I have been preparing for the GMAT for a while and although I have used both the GMAT Review and Quant Review and the likes of McGraw Hill, the Princetown Review, Kaplan etc your stuff was by far the best printed resource I used. I have bought and used it all and it has been invaluable.

I took the test yesterday and scored 740, which I am very happy with - so thanks.

Ryan scored the magical 700!

I'm sure you hear this all the time, but I just wanted to thank you for creating such a great, concise, easy to read GMAT package. Of all the GMAT books I purchased, your books - I bought both - were the most concise and effective.
I just returned from taking the exam and received a 700 score...not bad for someone who historically has been pretty poor at math (no longer!).

Teri wrote to me only four days after buying Total GMAT Math:

I've only gone through 3 sections in Total GMAT Math and it has already proved to be worth it's weight in gold. Thank you for this outstanding guide!

Leila can't be beat for hard work:

I absolutely adored your study materials. They were so helpful and I am grateful that your problems are a resource for gmatters. I mentioned before that I literally did all 1800 problems (am I the only weirdo who thinks that permutations and probability questions are fun?), and I read each answer explanation as well.

James is applying to b-schools now that he's armed with his 680:

Again, thanks for your advice and best of luck with your GMAT tutoring. Your methods and resources are definitely the best out there.

Iesan used my resources to go from a darn good score to a great one!

Just wanted to say that your Total GMAT Math & challenge materials were extremely helpful. I went from a 670 to a 730 this past November. In fact, my quant went from a 39 to a 47. Thanks!

Tanuj came home from the GMAT with a 710--pretty good after starting with a 570!

I took my GMAT on Dec. 6th and received a 710 (Q48, V38). My first diagnostic test was a 570 - a free online Princeton Review test. To be fair, I have never seen Data Sufficiency problems, so that may have affected by diagnostic score.
Your Total GMAT Math was the only math resource I needed other than the last 100 questions in each section of the OG, and repeating the GMATPrep software tests over and over for new problems. Really amazing resource and worth every penny.

Frank used my materials to get over the 700-score hump:

Your Total GMAT Math rocks! I followed your advice on setting a 2-hr per day schedule, studying the OG and of course Total GMAT Math. Happy to report that my score increased from 670 to 710. Thanks for all the helpful tips in your blog.

Ian used several of my resources, and landed a score starting with a seven:

I want to thank you for the GMAT materials you've developed! I took the GMAT today, and I scored a 710, which is a bit lower than I was aiming for, but I'm sure it's about 200 points higher than any score I would have received without the help of your books :) I would recommend your books to anyone studying for the GMAT! Thank you very much!

Whew! I hope that, soon, I can add you to this list.

One-on-one Tutoring Clients

In the past few months alone, several of my students have scored a 700 or higher, including a 750 and a 770! Here's what a few of my clients and readers have said about me.

Alex won't need to take the test again!

I just got back from the GMAT. I got a 750!
I wanted to say thank you for all of your help. The majority of my success on the test was due to our tutoring sessions. Not that you need it, but if you ever want a student to give you a reference for any reason, please let me know, I would be happy to.

Victoria took the test twice, and her second try came after a few months of hard work, including meeting with me 2-3 times per month:

Anyway my second and final score is...740!! Q48 V44. Thank you!

Adam improved his score from a 620 to a 690, and is now studying at Wharton:

Your tutoring was exactly what I needed to dramatically improve my score. Thanks again!

Jim hadn't looked at a math problem in nearly a decade, yet climbed all the way to a 680 on test day!

Thanks for all of you help over the last several weeks. I couldn't have gotten this far without it.

Kyle M. had taken the test before, but after several sessions with me, she got the score she needed to get into the program of her choice:

I just want to let you know that I was accepted at Columbia Business School - Executive Program and will be attending this fall. Thanks again for all of your help with my GMAT. It's nice to know that all the hard work finally paid off :). I keep referring my friends to you for GMAT help, so hopefully you'll see some of our other friends soon too!

Taylor met with me twice, and will never have to think about the GMAT again:

I re-took the GMAT and scored over 700, which was my goal. Columbia admitted me a few months ago, so I'll be heading there in the fall.

One meeting was enough to help Ray achieve his goal:

I took the test on Friday and boosted my score by 40 points to a 680. Although we never ended up meeting for a 2nd time, the information on your website, the OG explanations and your newsletters especially were very helpful.

After several weeks of tutoring, Jillian improved her score by more than 200 points!

I did it!!! Can you believe it? Thank you so much for all of your help. I could have never done it without you.

Everything Else

Tommy now has a 740 as part of his application package to schools such as Harvard:

My name is Tommy and I am currently a 2nd year medical school at UT Southwestern School of Medicine. I just wanted to thank you so much for all the free study materials you put up on your website, gmathacks.com, and let you know how much they have helped me along this process. I began studying for the GMAT about 3 three weeks ago and would have kept running into the same problems if not for your articles. They were particularly helpful for the advanced problems I encountered, which often required multiple approaches that weren't included in most of the GMAT practice books I bought. Your strong conviction is not resorting to picking numbers encouraged me to really think about the math problems (my weak area) and solve them more efficiently and effectively.

At the beginning of the process, I had a stack of 5 books to work with, but by this last week, your website was one of the only two resources (along with beatthegmat) I was consulting. Today, I took what started out as a 640 on practice tests to a 740 (48 math, 42 verbal) on the actual GMAT, and I just wanted to thank you for offering these resources for free. Beyond the immediate success, what this score means to me is a chance to be a competitive candidate for some of the New England schools closer to my family and also to potentially attend HBS with my best friend, who has already been accepted and is also a second year medical student to continue some healthy policy projects we embarked on during our college years at Rice.

I will be sure to recommend anyone and everyone considering the GMAT to your site and if there is anything I can do to help or contribute to gmathacks.com, please let me know.

Kim found that my Number Properties: Challenge set came in handy on test day:

750 on my 2nd attempt! Much thanks to offering the number properties challenge, it really helped me in a couple killer questions. All of the tips on your website were also incredibly useful, I referenced the tips list several times over the course of my study.

Pierre was able to put my advice to good use:

You have the best website out there discussing the GMAT, from its layout to the diversity of topics covered. Your explanations are clear and to the point which is refreshing considering the amount of useless info one has to go through in order to get to something interesting on other websites. Following some of your guidance I got a 680 today on the test.

Kyle S. scored nearly as well as I did:

Thanks for your GMAT tips blog. I just took the test today and using a combination of two books (the kaplan gmat and gmat 800 books) and your blog, I scored a 760! I couldn't have done it without your advice.

I always love triple-digit GMAT score increases! Mike wrote in with his story:

I found your site to be an excellent source of information in preparation for the GMAT. I first took the GMAT last Feb. and did not score well. The problem was the material and method I used to study. After several months of preparation and utilization of tips from your site - like purchasing the Official GMAT Guide, avoiding long division, and factoring - I improved my score by 130 points. I also found your guidance to be very positive in nature yet honest in helping me establish a realistic score goal.

Jessica found that my advice was the missing link:

First of all, I want to say thank you for all of your great posts. I took the GMAT on December 30, and prepped using the Kaplan book/cd and math study guide. While I felt comfortable and ready for the material, I still felt like my test attitude and mental readiness were lacking. Your blog helped round out some of the edges and helped me look at the test differently. Reading your posts was like having my own coach, and I truly appreciate it. I didn't feel like I was alone on test day.

Ryan is ready to move on to the next step:

I again just wanted to extend my thanks for creating and maintaining the site. I took my test yesterday and achieved my goal. You're advice was complete and utterly sound, and I will be certain to recommend your site and study materials to any potential test taker.

Charles couldn't have done much better. In fact, if he ever wants a career change, perhaps he should consider GMAT tutoring!

Jeff, I just wanted to thank you for your tips and practice problems. They helped me get a 770 on the exam last Saturday. I will definitely recommend your site and your books to my friends who are studying for the GMAT.

Arthur discovered that my exclusive problem sets were exactly what he needed:

These banks of questions are excellent. I am finding them an enormous help.

Ryan K. recently earned a score that will get him strong consideration at whatever business schools he applies to:

With much help for your website and practice problem sets I scored a 750. Thanks so much for all you do - it is very much appreciated. In fact, I've got a few of my co-workers hooked on your site.

Kareem looked far and wide for quality GMAT advice on the web, and finally found it here:

There are alot of GMAT related websites on the web but your site is by far the best. You give honest advice and tips that will work.

Cherian says:

I just wanted to drop in a short note thanking you very, VERY much for this wonderful website and the excellent insight and information you have in it. It makes my preparation for the GMAT go in the right track.

Tell Me Your Success Story!

If my resources or tips have helped you meet your goals of scoring well on the GMAT and getting into the business school of your choice, drop me a line. I'd love to hear about it!