How Our Calculators Work

Calculation principles

Our calculators use explicit mathematical formulas implemented as independent calculation functions. The calculation logic is strictly separated from the user interface so results do not depend on how a page is displayed.

Input validation

Inputs are validated before calculations are performed. Each tool defines its own mathematical constraints. For example:

• attendance counts must be whole numbers
• marks may contain decimals
• grade scores may exceed 100% when extra credit is possible
• invalid denominators such as division by zero are handled explicitly

Precision and rounding

Calculations are performed using the underlying numerical values rather than values rounded for display. Where possible, the calculation engine preserves the full result and rounding is applied only when displaying the answer.

Some tools intentionally do not round at all. For example, Marks Required to Pass may return a decimal mark because different institutions use different marking increments and rounding policies.

For calculations that depend on exact thresholds, we use small numerical tolerances where necessary to prevent floating-point representation from incorrectly classifying mathematically equivalent values.

Boundary cases

Some calculations have mathematically undefined or context-dependent cases. Instead of displaying misleading values, our calculators represent these cases explicitly.

Examples include:

• percentage change from an original value of zero
• attendance targets that cannot be reached
• required exam scores greater than the marks available
• grade weights below or above 100%

Local processing and privacy

For tools marked “Runs locally in your browser,” calculator inputs are processed by code running in your browser and are not uploaded or stored by us.

Our analytics infrastructure tracks page views and feature usage, but intentionally excludes the actual numbers, scores, and names you enter into the tools.

Testing and verification

Calculation engines are tested independently from the interface. Automated calculation tests cover standard calculations, decimal inputs, zero values, invalid inputs, boundary conditions, and tool-specific edge cases.

The full application is also checked with TypeScript and a production Next.js build before a calculator is published.