Methodology: How Our Calculators Work
This page explains how every SemesterMath calculator works: which grading scales it uses and where they come from, the formulas, how results are rounded, and how each calculator is tested.
1. Grading scales come from published sources
A GPA is only as right as the table that turns letters into grade points. Schools differ, so we don’t invent a “standard” table. Each scale is copied from a named source, stored as a data file with the source’s address and the date we last checked it, and listed below. Where sources leave a gap, we say how we filled it.
Course weights (the extra points for honors and AP classes) are not the same everywhere either. The default, 0.5 for honors and 1.0 for AP, IB and college classes, is North Carolina’s statewide rule. You can change both numbers on the high school GPA calculator to match your school.
College Board 4.0 chart (A 90–100, B 80–89, C 70–79, D 65–69)
| Grade | Percent | Grade points |
|---|---|---|
| A | 90–100 | 4.0 |
| B | 80–89 | 3.0 |
| C | 70–79 | 2.0 |
| D | 65–69 | 1.0 |
| F | below 65 | 0.0 |
Source: College Board BigFuture: How to Convert Your GPA to a 4.0 Scale, checked October 18, 2026. College Board calls this one commonly used system and says your school may differ. Its chart lists D as 66–69 and E/F as below 65, which leaves 65 itself unassigned; we count 65 as a D. The chart has no plus or minus grades, so B+ counts as a B on this scale.
Plus/minus scale (A 93–100, A- 90–92 … D- 60–62), as used by Green Bay Area Public Schools, Wisconsin
| Grade | Percent | Grade points |
|---|---|---|
| A | 93–100 | 4.0 |
| A- | 90–92 | 3.67 |
| B+ | 87–89 | 3.33 |
| B | 83–86 | 3.0 |
| B- | 80–82 | 2.67 |
| C+ | 77–79 | 2.33 |
| C | 73–76 | 2.0 |
| C- | 70–72 | 1.67 |
| D+ | 67–69 | 1.33 |
| D | 63–66 | 1.0 |
| D- | 60–62 | 0.67 |
| F | below 60 | 0.0 |
Source: Green Bay Area Public Schools (WI): Grading Scale, checked October 18, 2026. Green Bay gives the plus and minus grades in thirds of a point (A- 3.67, B+ 3.33); many schools round these to 3.7 and 3.3, so check your own handbook. F* (fail, no credit), P (pass), INC (incomplete), MX (medical excuse) and NG (no grade) are not counted in GPA. The page sets no honors or AP weighting: the weighting boxes in the calculator are your school's rules. Not counted in GPA: F*, P, INC, MX, NG.
10-point scale (A 90–100, B 80–89, C 70–79, D 60–69), as used statewide in North Carolina
| Grade | Percent | Grade points | Honors | AP / IB / college |
|---|---|---|---|---|
| A | 90–100 | 4.0 | 4.5 | 5.0 |
| B | 80–89 | 3.0 | 3.5 | 4.0 |
| C | 70–79 | 2.0 | 2.5 | 3.0 |
| D | 60–69 | 1.0 | 1.5 | 2.0 |
| F | below 60 | 0.0 | 0.0 | 0.0 |
Source: Onslow County Schools (NC): Grading Scale, under NC State Board of Education policy GRAD-009, checked October 18, 2026. Quality points: standard A 4, B 3, C 2, D 1, F 0; honors add 0.5; AP, IB and college (CCP) courses add 1.0; an F earns 0 at every level. Weights: Source: NC Department of Public Instruction: AP/IB/CIE Coursework, checked October 18, 2026. "The state course weighting system awards the equivalent of one (1) quality point to the grade earned in an AP/IB/CIE course." The 0.5 honors weight is from the Onslow County table above.
4.0 scale with plus and minus grades (A+ = 4.0)
| Grade | Grade points |
|---|---|
| A+ | 4.0 |
| 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 | 0.0 |
Source: UC Santa Cruz General Catalog: Grade Points, checked October 18, 2026. The same values (A 4.0, A- 3.7 ... D- 0.7, F 0) are used by Indiana University and the University of Tennessee. P and NP are not counted in GPA; I and IP carry no grade points until a final grade replaces them. Not counted in GPA: P, NP, I, IP.
2. Formulas
| Calculator | Formula |
|---|---|
| GPA | Σ(credits × grade points) ÷ Σ(credits). Pass/fail and incomplete grades are left out. |
| High school GPA | Unweighted: as above. Weighted: the honors or AP / IB / college bonus is added to each grade above 0 before averaging; an F earns 0 at every level. |
| Cumulative GPA | (current GPA × current credits + term GPA × term credits) ÷ (current credits + term credits). |
| Final grade | Score needed = (target − current × (1 − w)) ÷ w, where w is the final’s share of the grade. After the final: current × (1 − w) + final score × w. |
| Weighted grade | Σ(weight × score) ÷ Σ(weight), over categories that have both a weight and a score. A score like 46/50 is turned into a percentage first. |
| GPA raise | GPA needed = (target × (current + new credits) − current GPA × current credits) ÷ new credits. Credits of A’s needed = current credits × (target − current GPA) ÷ (top grade − target). |
| Test grade | (questions − missed) ÷ questions × 100; the letter comes from the chosen scale. The grading chart repeats this for every possible number missed. |
| Grade curve | Add points: score + (target − top score). Scale: score × target ÷ top score. Square root: 10 × √score. Shift the average: score + (target average − class average). Flat and average curves are capped at 100% unless you keep higher scores. Which curve to use is the teacher’s choice, not a fixed rule. |
| Scale converter | Looks the grade up on the chosen scale: a letter gives its grade points and percentage range; a percentage gives its letter; grade points give the matching letter, or the two letters a GPA falls between. |
| Class rank | Top % = rank ÷ class size × 100. Lowest rank inside the top p% = class size × p ÷ 100, rounded down. Schools set their own rules for ties and borderline cases; the Texas top-10% admission law is cited on the page. |
3. Reading what you type
- Letters (B+, b+ or B +) are matched to the chosen scale. If the scale has no plus or minus grades, a B+ counts as a B and the calculator says so.
- Percentages (88 or 88%) are turned into a letter with the scale’s cut-offs. Scales without published cut-offs ask for letters instead.
- Grade points (3.3) are used as they are. A number above the scale’s top grade is refused rather than guessed at, because it is usually an already-weighted grade.
- Pasted grade lists (from Canvas, PowerSchool, a report card or a spreadsheet) are read line by line in your browser: the course name, its grade and, if shown, its credits. Where a portal shows both a percentage and a letter, we keep your school’s letter. Where a line has a grade for each term, we use the last one. Lines we can’t read are listed with the reason, and credits that weren’t in the text are filled in for you to check. Nothing you paste is sent to us or saved.
4. Rounding
GPAs are shown with two decimals and percentages with up to two (87.33%, 104%), rounded half up (3.145 shows as 3.15). The calculation itself keeps full precision. Some registrars cut off extra decimals instead of rounding, so a transcript can differ in the last digit.
5. Testing
Each calculator has a set of hand-worked test cases: the worked example on its page, edge cases such as zero credits, pass/fail grades or a target above 100%, and a case for each scale it offers. The arithmetic for each case is written out by hand first, and the calculator must reproduce every number before it is published. The example numbers and tables on each page are then printed from the calculator’s own tested output, so the page and the live result cannot disagree.
6. What the calculators don’t know
School-specific rules such as grade replacement for retaken courses, an A+ worth 4.3, capped weighted GPAs or colleges recalculating your GPA can’t be guessed. Each calculator page says which rule it applies. Your school’s transcript is always the official figure.
7. Corrections and reviews
Sources are re-checked before each term, and each calculator shows the date it was last checked. If you find an error or your school uses a different scale, please contact us.