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How would I be able to calculate my overall average grade (or grade point average) for these courses?

Course Course Credit (weight) Course Grade
Biology 101 45 86
Psychology 210 30 74
Chemistry 250 45 88
English 200 60 77

My understanding is by simply adding the course grades column together and dividing by the total cumulative possible marks.

(86+74+88+77)/400 = 0.8125

But this number seems very strange in the 0 to 4 GPA.

Maldred
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    It's probably better for you to ask the Administration Office for this kind of problems. However, assuming it is similar to my usual understanding of credit point, you should multiply convert your score into 0-4 scale first. – Evan William Chandra Feb 08 '21 at 07:50

2 Answers2

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You calculated an unweighted GPA. To weight it, you must factor in the course credit variable.

> sum=45+30+45+60
> (86*45+74*30+88*45+77*60)/sum
[1] 81.5

As the original units are in a 0-100 scale, your weighted gpa is about a B-.

To convert to a 4.0 scale, simply use the appropriate unit conversion

> 81.5*4/100
[1] 3.26

Your original calculation was missing a multiplication by 4. The procedure for your unweighted gpa should be

> (86+74+88+77)/4*4/100
[1] 3.25
Vons
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  • Is it necessary to include the division of 4 and the multiplication of 4 here? Seems redundant? Is that just used for clarification? – Maldred Feb 08 '21 at 08:03
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    Of course they cancel out, but the first calculates the unweighted average of your gpa and stands for 4 classes, and the second is part of the unit conversion factor (4.0/100). If you had 5 classes, and in the fifth class you scored a 90, the unweighted formula would be (86+74+88+77+90)/5*4/100. – Vons Feb 08 '21 at 08:05
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To calculate weighted GPA, multiple each grade on a 4.0 scale by the weight of the course and then find the average.

The conversion of 0-100% grades to a 0.0-4.0 scale may be calculated differently at different institutions. You need to check with your institution to see exactly how they do it. However, almost no institution directly scales 0-100% to 0.0-4.0 proportionally. Instead, 0-100% is divided into discrete sections, each of which is then mapped to a specific point value.

The most common system in the United States uses sections of size 10% for grades of 60% or higher, and gives no points for grades lower than 60%, which are considered failing:

  • 90-100% -> 4.0
  • 80-89% -> 3.0
  • 70-79% -> 2.0
  • 60-69% -> 1.0
  • 0-59% -> 0.0

Under this system, your grades would convert as follows:

  • 86% -> 3.0
  • 74% -> 2.0
  • 88% -> 3.0
  • 77% -> 2.0

And your weighted GPA would then be:

(45 * 3.0 + 30 * 2.0 + 45 * 3.0 + 60 * 2.0) / (45 + 30 + 45 + 60) = 2.5

Another common system uses sections of size 5% instead of 10%:

  • 95-100% -> 4.0
  • 90-94% -> 3.5
  • 85-89% -> 3.0
  • 80-84% -> 2.5
  • 75-79% -> 2.0
  • 70-74% -> 1.5
  • 65-69% -> 1.0
  • 60-64% -> 0.5
  • 0-59% -> 0.0

Under this system, your grades would convert as follows:

  • 86% -> 3.0
  • 74% -> 1.5
  • 88% -> 3.0
  • 77% -> 2.0

And your weighted GPA would then (rounded to three digits after the decimal point) be:

(45 * 3.0 + 30 * 1.5 + 45 * 3.0 + 60 * 2.0) / (45 + 30 + 45 + 60) ≈ 2.417

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