How Letter Grades Usually Work: Weightage, Marks and Instructor Cutoffs

Every semester has a version of this conversation: someone scored 89, someone else scored 90, and the group chat decides that one is an A and the other is a tragedy. Sometimes that is true. Often it is folklore. Letter grades are produced by a chain — marks become percentages, percentages meet cutoffs, letters become grade points — and every link in that chain is controlled by your course and your institution, not by universal law.

This guide walks the chain generically and explains where the movable parts are. The recurring instruction — check your course outline — is not a disclaimer; it is genuinely the answer to most grading questions.

Step one: marks become a percentage through weightage

Coursework is almost always weighted. A quiz worth 5% and a final worth 45% both produce percentages, but they influence your course total very differently. The arithmetic is:

Contribution = (marks earned ÷ marks total) × weight

Consider a course midway through the semester:

| Component | Earned / total | Percentage | Weight | Contribution | |---|---|---|---|---| | Quizzes | 8 / 10 | 80% | 5% | 4.00 | | Assignments | 25 / 30 | 83.3% | 10% | 8.33 | | Sessional | 40 / 50 | 80% | 15% | 12.00 | | Midterm | 30 / 40 | 75% | 25% | 18.75 |

Secured so far: 43.08 points out of the 55 the graded components are worth. The final carries the remaining 45%, so the course is not lost or won yet — a fact worth keeping in perspective during midterm season. The course total calculator does this arithmetic for you and flags when entered weights do not add up to 100, which usually means an assessment is missing or mistyped.

Step two: percentages meet cutoffs

A cutoff is the minimum percentage for a letter. This is where universality ends. Some institutions publish one table for the whole university; some let each course set its own; some apply relative grading, where letters are assigned partly by position in the class. A table that is correct in one course can be fiction in another — sometimes fiction by several points, occasionally by a full letter.

Practical consequences:

• Read the assessment's own scheme. The course outline (or its grading section) is the document of record.
• Ask about curves early, not after results. If relative grading is used, the same 78% can be an A in a hard term and a B in an easy one.
• Do not import cutoffs from a friend's course. It is the most common source of avoidable anxiety.

What a curve actually is

“Curving” is an umbrella word for several different policies, and they are worth telling apart. A scale adjustment shifts every cutoff (a 90 becomes an 87, say). A rank-based or relative curve assigns letters by position — a fixed share of A grades, for instance — which makes your letter depend on the cohort, not just on your score. A clamp raises the class's raw scores by adding marks to the highest-scoring question. The common thread: if any of these are in play, your percentage is an input, not a verdict, and the only reliable local information is what the course tells you explicitly. Ask which policy applies before optimising against last year's numbers.

Step three: letters become grade points

Once a letter exists, your institution's scale assigns it grade points — for example 4.00 for an A, 3.67 for an A−, 3.33 for a B+ on a common 4.0 arrangement. Those points are what the GPA machinery actually consumes; the letter is the label, the point is the currency. The grade point converter shows the translation on an editable scale, including the quality points a course contributes.

Two details worth knowing:

• Plus/minus steps are not uniform across institutions. A− might be 3.67 or 3.70; B− might be 2.67 or 2.70. Small differences, compounded across a degree.
• Some grades are outside the scale entirely. Pass/fail, audited courses, incomplete grades and withdrawals usually do not carry grade points — but whether they consume credit hours varies by institution.

FAQ

Is 90% always an A?

No. It is a common cutoff, not a global one. Some institutions set 85, some 93, some vary by course or apply curves. The percentage-to-letter mapping is exactly the part of the chain you must source locally.

Does a curve punish strong students?

Not inherently. Relative grading can compress or lift scores depending on the cohort and the instructor's method. What it does mean is that your letter is not fully determined by your raw percentage — which is worth knowing before you set a target based on last year's numbers.

My course outline does not state cutoffs. What now?

Ask the instructor or teaching assistant directly, and ask early. If no table exists, assume relative or instructor-set grading and focus on maximizing the components you control. The final grade calculator still works — it targets a percentage; the letter mapping is the part that stays with your course.

The takeaway

Marks become percentages through weightage, percentages become letters through cutoffs, and letters become points through your institution's scale. Two of those three steps are local rules, which is why generic advice stops at the arithmetic. Master the arithmetic with the CGPA calculator, and source the rules from the only documents that own them: your course outline and your institution's handbook.