The tools in this section share a theme: they answer the questions people actually get wrong. Percentage change measured against the wrong base. Fraction addition without a common denominator. Ages and deadlines miscounted because months are irregular and leap years exist. A GPA averaged without credit weights. Each calculator is built around the correct convention, states it on the page, and shows a worked example.
For students, the grade tools close the loop between "what did I get" and "what do I need": convert any score to a percentage and letter grade, and compute exactly what a final exam requires — including the cases where the honest answer is "already secured" or "not reachable, here is the plan instead". Teachers and parents are welcome to check our work; the formulas are printed on every page.