IQ Tests

Hoeflin IQ Tests

Hoeflin Letter Series Test

These 12 letter series problems were created by Ronald K. Hoeflin, Ph.D., philosopher and creator of the famous Mega, Titan, Ultra, and Power tests, and founder of several high IQ societies that you will find listed on

While knowledge of certain things may give you an advantage on this test, the primary focus is on lateral and logical thinking and problem solving. Thinking "outside of the box" in the right ways will allow you to solve most of the problems. No advanced mathematical knowledge is needed to solve any of the problems (not even algebra).

Unlike most of our tests, you are encouraged to use a dictionary in book form, especially an unabridged dictionary such as Webster's Third New International Dictionary: or at least a "good" dictionary such as Merriam-Webster's Collegiate Dictionary, 11th Edition:, and you may use Please do not use any other books, web sites, software, or the help of anyone else in working these problems. You may use scrap paper, pen or pencil, and a standard or computer calculator.

For each problem, determine which letter should replace the question mark (?).

Many of the problems are VERY difficult, and several may contain words, names or terms with which you are unfamiliar. Be sure to answer every problem, even if this means guessing on some problems. There are no penalties for guessing.

Although there is no time limit, try to complete the test in 1 or 2 sessions.

Your estimated IQ score, general population percentile ranking, and the answers to the problems are all provided when you complete the test.
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(Please note: Your score can only be recorded the first time you take a test. Subsequent scores will not be saved)