Calculation Methodology

Numeric policy

Calculations use JavaScript numbers at full available precision and round only for display. Users can choose 0, 1, or 2 displayed decimals. Letter grades use the unrounded percentage by default unless round-before-letter is explicitly enabled.

• Blank inputs are missing, never automatic zeros.
• Zero denominators, nonnumeric values, and negative possible points are rejected.
• Scores above 100% require an explicit bonus or unclamped context.
• Weights are never silently normalized.

Core formulas

Percentage: earned ÷ possible × 100. Equal average: sum of percentages ÷ count. Points average: total earned ÷ total possible × 100. Weighted contribution: sum of score × weight ÷ 100. Semester grade: sum of grade × weight ÷ sum of included weights, with an explicit current-estimate notice when the entered structure is below 100%.

Required final: (target − current × (1 − final weight)) ÷ final weight. Projected course: current × (1 − final weight) + final score × final weight.

Curve formulas are displayed directly beside the tool. Z-score rescaling uses population standard deviation because the entered class list is treated as the full population. Distribution statistics use the sorted entered population; quartiles use linear interpolation between adjacent ranks.

Default letter scale

The editable example thresholds are A+ 97, A 93, A− 90, B+ 87, B 83, B− 80, C+ 77, C 73, C− 70, D+ 67, D 63, D− 60, and F below 60. This is not a universal policy.

Public acceptance cases

Representative checks include 17/20 = 85.0%; 42/50 = 84.0%; 80, 90, and 100 average to 90.0%; current 88, target 85, final 30% requires 78.0%; 90 at 40% plus 80 at 60% equals 84.0%; quarters 86 and 92 at 40% plus final 80 at 20% equals 87.2%; and the square-root curve maps 64 to 80.0%.

• Required-final targets above 100% are reported as impossible under the model.
• All-identical curve scores block z-score division by zero.
• Malformed share fragments are discarded safely.
• Exports retain displayed precision and active assumptions.

Review and corrections

Formula changes require a matching unit test and route acceptance check. Corrections are reviewed against the published formula, reproducible inputs, and the controlling school policy when relevant. Material changes update the last-reviewed date.