The letter on a report card feels like a fact. It isn’t — it’s a lookup. The percentage is the measurement; the letter is whatever scale the school decided to lay over it, and American schools have never agreed on one scale. Understanding which scale you’re grading on matters more than the math itself, because the math is trivial and the scale is a policy choice.

Where A–F came from

Letter grades are younger than the public school system. Through most of the 1800s, American schools reported percentages or verbal judgments (“good”, “middling”). The letters arrived with the research university: Harvard experimented with class divisions in the 1880s, and Mount Holyoke published the first recognizable A–E letter scale in 1897 — A for 95–100%, E for below 75%. By the 1940s the five-point A–F version had swept the country, riding the same wave as IQ testing and standardized sorting.

Two accidents of that history stuck. First, E disappeared — partly so the failure letter read unambiguously (“F” for fail, never confusable with “excellent”), partly because four passing letters looked cleaner. Second, the percentage cutoffs were never standardized. Mount Holyoke’s A began at 95; most modern schools start it at 90.

The three scale families in real use

Ask five teachers what a B is and you’ll get three answers. Nearly every US grading policy reduces to one of these:

Letter rung	Standard (10-pt)	Strict (7-pt)	Lenient
A+	97–100	98–100	95–100
A	93–96.9	95–97.9	90–94.9
A−	90–92.9	93–94.9	85–89.9
B+	87–89.9	91–92.9	82–84.9
B	83–86.9	88–90.9	78–81.9
B−	80–82.9	85–87.9	75–77.9
C+	77–79.9	83–84.9	72–74.9
C	73–76.9	80–82.9	68–71.9
C−	70–72.9	77–79.9	65–67.9
D+	67–69.9	75–76.9	62–64.9
D	63–66.9	72–74.9	56–61.9
D−	60–62.9	70–71.9	50–55.9
F	below 60	below 70	below 50

These are the exact thresholds the grader uses — switch scales there and watch a 75% move from C to D+ to B−.

Standard is the default for a reason: ten-point bands are easy to remember and a 60% pass line lets a student recover from a bad unit. Strict — the “7-point scale” — survives in districts that want A to mean near-mastery; the practical effect is that the pass line jumps to 70 and every band narrows, which squeezes students who hover near boundaries. Lenient covers systems where the floor is higher: an A from 85 and a pass at 50 appear in standards-based grading, in several Canadian provinces, and anywhere “minimum F = 50” policies apply, on the theory that a 0–49 hole is statistically unrecoverable and mathematically cruel.

Plus/minus: a second scale riding on the first

The +/− refinements split each band roughly into thirds — the bottom third gets the minus, the top third the plus. They came later than the letters (widespread by the 1970s–80s, driven by colleges wanting finer GPA distinctions) and they’re still optional: plenty of K-12 districts issue flat A/B/C/D/F. Where they exist they matter at boundaries — 89.9 is a B+, not an A−, and that sliver is why “can you round my grade?” is a permanent feature of teaching.

Letter → GPA points

Colleges and gradebooks convert letters to a 4.0 scale: A+/A = 4.0, A− = 3.7, B+ = 3.3, B = 3.0, B− = 2.7, C+ = 2.3, C = 2.0, C− = 1.7, D+ = 1.3, D = 1.0, D− = 0.7, F = 0. Two wrinkles: some schools count A+ as 4.3 (uncapped), and weighted courses add a point or half-point for AP/IB/honors — which is how a 4.7 GPA happens. The grader’s optional GPA column uses the standard unweighted values.

What actually matters for grading

The scale is a syllabus decision, and the honest move is to declare it: thresholds, whether you round (89.5 → 90?), and whether D earns credit. Students don’t fail because the scale was strict; they fail because the scale was a surprise. Whatever you pick, the printable chart on the homepage will match it — print the version you actually grade by.

Frequently asked questions

Is 89.5% an A- or a B+?

On the standard scale, 89.5% is a B+ — the A- rung starts at 90. Whether it *should* round up is a policy question: many teachers round 89.5 to 90 before grading, others never round. The consistent rule is to pick one convention, put it in the syllabus, and apply it to every student identically.

Why is there no E grade?

Mount Holyoke's original 1897 scale did use A–E. Schools dropped E for two reasons: F reads unambiguously as 'failed' while E could be mistaken for 'excellent', and a five-letter scale with F at the bottom left a tidy gap between passing (D) and failing. A few districts kept E — which is why some transcripts show it — but F won nationally.

Do colleges care which scale my school uses?

Mostly no — admissions offices recalculate GPA on their own scale or read the transcript next to the school's published grading policy. A B+ earned on a strict 93-is-an-A scale reads differently than one on a lenient scale, and counselors' school profiles explain exactly that.

What's the difference between A and A+ for GPA?

On the standard unweighted 4.0 scale, both are 4.0 — A+ is capped. Some schools run an uncapped scale where A+ counts 4.3, which is how GPAs above 4.0 appear on transcripts even before weighting for AP or honors courses.

Is a D a passing grade?

Usually, but with an asterisk. D- (60–62.9 on the standard scale) earns credit in most US schools — yet often doesn't count for prerequisites, major courses, or graduation requirements that specify 'C or better'. Passing the class and passing the requirement are different questions.