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How the categories are organized

Categories follow the kind of question you are asking, not the formula behind it. Loan payments and savings targets both use compound interest, but they sit in Finance because they answer money questions. Pakistan salary tax, government pension and gratuity have their own Salary & Pension category because they apply specific published rules. Zakat, Fitrana and Ushr are grouped under Islamic, where the arithmetic is kept separate from the religious ruling.

If you are not sure where a tool lives, use the search on the all calculators page, or start from a task in Collections. For longer worked cases, the articles walk through real examples step by step.