Equivalent Grading System

Revised 12/21/14

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The following grading system precisely equates rubric, point, letter, and percentage grades using the following equation:

Rubric Base and Quality Points = (Percentage – 55) x 0.1

Excellent 4 4.00 A 95 93.33 – 100.0
3.67 A- 92 (91.7) 90.00 – 93.32
Above Average
to Average


3.33 B+ 88 (88.3) 86.67 – 89.99
3.00 B 85 83.33 – 86.66
2.67 B- 82 (81.7) 80.00 – 83.32
Satisfactory to
Below Average


2.33 C+ 78 (78.3) 76.67 – 79.99
2.00 C 75 73.33 – 76.66
1.67 C- 72 (71.7) 70.00 – 73.32
Minimum Pass 1 1.00 D 65 60.00 – 69.99
Failure 0 0.00 F 55 50.00 – 59.99

Percentage grades over 100 are averaged as 100
Percentage grades under 50 are averaged as 50


Grades are typically given in a 5-step, or more, letter scale (A, B, C, D, and F) but translated into a final 41- or 401-step quality point score (0 – 4.0/0) for averaging. Schools typically set letter grades and their point equivalents. Many faculty, however, use a 101-step percentage point score (0 – 100) some or all of the time for assigning or averaging grades before determining a final letter or point grade. To the consternation of some students, faculty members are typically free to use their own percentage system with most opting for what can be called traditional 7- or 10-point grading scales.

Since the final arbiter of a student’s academic achievement is generally his or her point score, one could argue the most appropriate percentage system is one that most accurately mimics point scores. One could multiply each quality point by 25 to create a percentage system but that, of course, represents no academic challenge. Multiplying points by 10 and assigning them to the top of the percentage system (from 60 – 100) puts one closer to the mark but a direct translation would mean an A could only be achieved by the near impossible feat of averaging 100. Therefore, devising a percentage system that works down from 100 instead of up from 60 is best.

When counting quality points by 10ths, there are 10 steps between full grades. Therefore, when counting down from 100, assigning 10 percentage points to each full grade range is logical.

Because 0 is its own step on the grading scale, there is an extra point for the entire grading range that can either be assigned to the A range or the F range. Assigning it to the A range (90 – 100) translates better to quality points when minus/whole/plus grades are used, and is the typical convention.

Dividing full grades into minus, whole, and plus grades is more precise and, so, should be specified in a grading system. Its inclusion, however, does not require instructors or institutions to give plus or minus grades for either assignments or final grades. In particular, one could imagine an instructor–who prefers full grades–returning assignments with full grades but then submitting an averaged minus/whole/plus final grade.

Many institutions do not use A+, D+, and/or D- grades. In such cases, those ranges can be added to the respective whole or full grade. Conversely, those grades can easily be created following the conventions used for B and C grades.

Dividing full grades by 3 creates minus/whole/plus grades, but it also leaves an extra point that must be assigned to a range. Assigning it to the whole range better mirrors quality points, and is logical.

Calculating each percentage point in 100ths better mirrors quality points when using minus/whole/plus grades, is more accurate, and makes the differences between the placements of extra points marginal. While this does move 73, 83, and 93 from their typical positions as whole grades to minus grades, in an era of grade inflation that can be seen as an advantage.

In combining grades that originate as letters with other letter grades and percentage scores, it is necessary to assign each grade a number. Using a percentage equivalent score rather than a point score is sometimes simplest because grades originating as percentages do not need to be converted for averaging.

Dividing full, minus, whole, or plus grade ranges by 2 and rounding the result to a whole or 10th place number creates percentage equivalent grades that can be equated to point and letter grades. The result is an exact mapping of quality point scores from 55 – 95 percentage points using the formula: Rubric Base and Quality Points = (Percentage Equivalent – 55) x 0.1.

As in quality points, with this system if an F is averaged with an A the result is a C. This becomes problematic, however, when a missing letter grade assignment is combined with a missing percentage grade assignment. Each would receive an F but one could be averaged as a 55 while the other could be averaged as 0. Therefore, if both letter and percentage grades are used, percentage grades less than 50 should be averaged as 50 (5 points below the F percentage equivalent). Conversely, to maintain parity, the maximum percentage grade should be 100 (5 points above the A percentage equivalent). An exception to the lower limit could be made in the case of cheating, so there is a simple and tangible penalty beyond that suffered for missing or poor work.

If a five-step rubric is created with 0 to 4 possible points, it can be directly equated to quality points and, hence, percentages. If the total value of a rubric equals forty points, for instance, ten areas with 0, 1, 2, 3, or 4 points, or five areas worth 0, 2, 6, or 8 points, then the total can be directly equated to percentages by adding 55.

Finally, the suggested overall performance descriptions are designed to straddle traditional definitions and inflated realities.

2 Responses to “Equivalent Grading System”

  1. Peter Kiwitt Says:

    You could divide the 40 quality points by the 6 point rubric, which gives you 6.66 per rubric point, and then add 55 ([40/6=6.66] x R + 55 = %). So, perhaps, 0 (cheating) = 0, 0 (missing assignment) = 55, 1 = 62, 2 = 68, 3 = 75, 4 = 82, 5 = 88, 6 = 95. If that’s too rigorous, you could select the letter grade you felt appropriate and then assign the percentage grade that goes with that.

  2. Sonja Miller Says:

    This makes sense. I now see why and how the 2 scoring system correlate. I almost hate to ask this question, but I’m going to anyway … Is there a way to convert 6 point rubric to a percentage equivalent?

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