Principles
- Calculations use full precision internally. Only the displayed number is rounded.
- Rounding is half up: GPAs to 2 decimal places (3.875 → 3.88), percentages to 1 decimal place (82.75 → 82.8).
- Letter grades are taken from the displayed rounded percentage, so the number and letter always agree (82.96% displays as 83.0% and is a B).
- Everything runs in your browser. Nothing you type is sent to a server.
Default grading scale
The default is the common US 4.0 scale with plus/minus grades: A+ and 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.
Default percentage cutoffs: A from 90%, B from 80%, C from 70%, D from 60%; below 60% is an F. Within each 10-point band, the lowest 30% of the band is a minus and the top 30% is a plus (for example, B− is 80–82.9%, B is 83–86.9%, B+ is 87–89.9%). A+ starts at 97%.
You can change all of this in any calculator’s scale settings: 4.0, 4.3 (A+ = 4.3) or 5.0 scales; plus/minus on or off; your own A–D cutoffs; and the Honors and AP/IB bonuses. If you tick “Remember my entries on this device”, your scale is saved in your browser and shared by all GradeHelm calculators.
If you set your own A–D cutoffs, plus/minus ranges are split the same way (lowest 30% of each band is a minus, top 30% a plus). Many schools that use custom cutoffs publish their own plus/minus ranges; if yours does, choose letter grades rather than typing percentages so the calculator uses your school’s letters exactly.
Formulas
GPA (semester, college or cumulative from classes)
GPA = Σ (grade points × credits) ÷ Σ credits
A class with a grade but no credits is skipped and listed under “Show the math”. If you enter percentages, each one is first converted to a letter with your cutoffs.
High school weighted GPA
Weighted GPA = Σ ((grade points + level bonus) × credits) ÷ Σ credits
Defaults: Regular +0, Honors +0.5, AP/IB +1.0. No bonus is added to an F. The high-school calculator always starts from a 4.0 (or 4.3) base and adds these bonuses per class, so the separate 5.0 scale setting isn’t offered there (it would count the AP bonus twice). On the GPA and cumulative calculators, the 5.0 scale setting adds 1.0 to every passing grade.
Cumulative GPA
New GPA = (current GPA × current credits + term GPA × term credits) ÷ total credits
GPA needed next term
Needed = (target × (current credits + next credits) − current GPA × current credits) ÷ next credits
If the result is above the scale’s maximum, the target is shown as not reachable, with the highest GPA you could reach.
GPA limits
A GPA you type in (current GPA, term GPA or target) can’t be higher than the top of your selected scale: 4.00, 4.30 or 5.00. On the cumulative GPA calculator you can tick “These are weighted high-school GPAs”; the limit then rises by the AP/IB bonus (to 5.00 by default), because weighted GPAs legitimately go above 4.0.
Required final exam score
Needed = (target − current grade × (1 − w)) ÷ w, where w is the final’s weight as a decimal
A result above 100% is shown as not reachable (with the best possible course grade). A result of 0% or less means the target is already secured.
Weighted grade and semester grade
Grade = Σ (score × weight) ÷ Σ weights
If the weights don’t total 100%, we divide by the weights entered and show a notice.
On the semester calculator, if you enter the exam’s weight but leave its score blank, the result is your grade before the exam (terms only). “What do I need on the exam?” then uses the exam’s share of the semester:
Exam share = exam weight ÷ (term weights + exam weight)
Needed on exam = (target − terms grade × (1 − exam share)) ÷ exam share
Points grade
Grade = total earned ÷ total possible × 100
Input limits
Credits: 0 to 60 per class (UK modules are often 15, 20 or 30 credits). Percentages and scores: 0 to 150% (to allow extra credit). Up to 100 rows per calculator. Invalid inputs are flagged next to the field with an explanation.
Testing
The calculation engine is tested automatically with fixed test cases, including every worked example on this site and edge cases such as empty input, boundaries between letter grades and floating-point rounding.
Limitations
Schools have their own rules for repeated courses, pass/fail grades, transfer credit, weighting and rounding, and those rules override any general formula. Treat our results as a planning aid and confirm important numbers with your school.
Spotted something wrong? Please tell us.