Welcome to GMAT Ninja!

Looking for an experienced private GMAT tutor in Denver or online? You’ve come to the right place.

We’re a pair of passionate, full-time, dedicated GMAT and GRE tutors, offering our services in Denver, Colorado – and anywhere there’s a good internet connection.

Charles Bibilos, GMAT Ninja founder, is one of the world’s most accomplished GMAT tutors, with the following qualifications:

  • over 15 years of GMAT and GRE private tutoring experience
  • perfect GMAT score of 800 (51Q/51V/6.0 AWA), earned in July 2011
  • perfect GRE score of 340, earned in December 2012
  • perfect scores on the SAT quant and ACT
  • experience teaching PhD-level statistics, undergraduate-level economics, and high school English and mathematics, in addition to a stint as an instructor for a major test-prep firm
  • hundreds of GMAT students successfully admitted to top MBA programs (HBS, Stanford, MIT, Wharton, Haas, Booth, Columbia, INSEAD, etc.)
  • Stanford University graduate with distinction
  • published author of test-prep curriculum
  • genuinely nice guy with a nuanced approach to GMAT tutoring

Michael Maietta, GMAT Ninja’s newest addition, developed his interest in tutoring more than a decade ago, and began tutoring full-time in 2015, after several successful years as a management consultant. Click here for more on Michael and his approach to tutoring.

For more on our tutoring or MBA admissions services—or to learn more about the GMAT and GRE in general—please visit the following pages:

And if you want to read unsolicited, online testimonials about my GMAT tutoring services, click here or here or here or here or here or here or here or here. Charles was even interviewed for a GMAT article in U.S. News & World Report, and Charles and Michael were recently appointed as GMAT Club’s resident GMAT verbal experts.

If you’re ready to get started, click here to learn more about GMAT tutoring, or email us at gmatninjallc (at) gmail (dot) com.

Thank you for visiting, and best of luck with your GMAT, GRE, and MBA goals!