How We Verify Calculations
Last updated: April 28, 2026
Teachers, students, and parents copy numbers from QuickGrade into real gradebooks and report cards, so every calculator has to match the math a teacher would do by hand. This page describes the formulas we use, the test cases we check against, and how we handle rounding.
The formulas we use
- Easy Grader —
percentage = (total − wrong) ÷ total × 100. Partial credit is supported by accepting decimal values for wrong answers. Deep dive: the grade percentage formula. - Weighted Grade Calculator —
Σ(score × weight) ÷ Σ(weight). Weights are normalized when they do not sum to 100%. See weighted grades explained. - Final Grade Calculator —
needed = (target − current × (1 − w)) ÷ w, where w is the final exam's weight as a decimal. Deep dive: the final grade guide. - Letter Grade Calculator — percentage bands from the standard US 10-point scale and plus/minus scale published on our grading scale chart.
- GPA Calculator —
GPA = Σ(gradePoints × credits) ÷ Σ(credits)using the common 4.0 scale. See the GPA guide.
Test cases we check
Every calculator is spot-checked against known worked examples before it ships and after every meaningful code change:
- Easy Grader: 20 questions with 3 wrong should return 85%; 25 questions with 0 wrong should return 100%; 30 questions with 30 wrong should return 0%.
- Weighted Grade: 90 at 40% + 80 at 60% should return 84.0%.
- Final Grade: current 82, target 90, final worth 25% should require 114 on the final (i.e. not achievable — the calculator flags this).
- GPA: A (4.0, 3 cr) + B (3.0, 4 cr) + C (2.0, 3 cr) should return 2.95.
Rounding and display
Internal math is done in full precision. Percentages are displayed with optional decimals so that borderline scores (for example 89.5%) do not silently round into a different letter grade. When a school uses a non-standard rounding rule, we recommend checking against the official rubric.
Reporting an issue
Found a case where our output disagrees with a gradebook or a worked textbook example? Please email us through the contact page with the exact inputs — we treat calculator accuracy as the highest-priority issue on the site.