Percentage to letter grade: example scale and school rules

Calculate the percentage before choosing a letter

Divide earned points by possible points and multiply by 100. For example, 17 points out of 20 gives 85%. Then look up 85 in the grading scale your teacher uses. Computing a percentage is arithmetic; assigning a letter is a policy choice. There is no single equation that makes 85% the same letter in every course. Use earned points rather than correct-question counts when questions have different values.

Percentage = earned points ÷ possible points × 100

• Calculate the percentage from assignment points
• Review points and percentage grading

Example percentage-to-letter-grade chart

The table below is Best Grade's default example scale for scores from 0% to 100%. Lower boundaries are inclusive: exactly 87% is B+, while 86.99% is B if the raw score is used. The plus/minus boundaries are not claims about your school's rules. Compare this chart with your syllabus before interpreting any score.

How to read the chart: 75%, 85%, and 90%

At 75%, the highest qualifying cutoff is C at 73%, so the example letter is C. At 85%, B at 83% qualifies but B+ at 87% does not, so the letter is B. At exactly 90%, A− qualifies but A at 93% does not. At 92.99%, the raw-score letter is still A−. At 93%, it changes to A. Check the minimum boundary, not whichever letter seems closest to your score.

• See the worked 15-out-of-20 example

Why one school's A can differ from another's

Calculator.net presents an example plus/minus scale with A beginning at 93%. Carnegie Mellon's teaching guidance includes a sample scale with A beginning at 90% and recommends checking departmental standards and communicating the chosen scale in the syllabus. These examples show why a percentage alone cannot determine an official letter. Your course may omit plus/minus grades or use a rubric instead of percentage bands. Best Grade's custom grading scale lets you replace the example minimums with your teacher's boundaries.

• Match the test grader's custom scale to your syllabus

Should you round before converting?

Follow the published rounding rule. Best Grade's test grader uses the unrounded percentage for the letter lookup; changing the display's decimal places does not change the letter. For example, 89.95% could display as 90.0% with one decimal but remains B+ on the raw example scale. A course that explicitly rounds to the nearest whole percent before assigning a letter could instead classify that score as 90%. University of Arkansas Grantham publishes its own final-grade rounding rule, illustrating that rounding is institution-specific. Never assume a display setting grants a higher official grade.

Convert a course average, not separate letters

Calculate the course's overall percentage using its points or category weights before applying the course's letter scale. Do not average letters such as A and C to invent a course percentage. A 90% test category weighted at 60% and a 70% homework category weighted at 40% yield 82%, which is B− on the example scale. If you need a GPA instead, use course letter grades and credits with your institution's grade-point mapping. Percentage bands and GPA points are related by policy, not interchangeable quantities.

• Combine category percentages and weights
• Calculate a credit-weighted GPA

What if your gradebook shows a different letter?

Check the exact raw score, cutoff scale, rounding order, assignment weights, and any dropped work or penalties. A missing assignment may be counted as zero, while an ungraded item may be temporarily excluded. Also check whether passing the final exam is required independently of the course average. If the difference remains, ask your teacher which published rule explains it. A calculator is a checking tool, not a replacement for an official gradebook.