A template is the right answer when your problem is a blank page — you know which numbers you want to track but not how to lay them out. It is the wrong answer when a workbook already exists and is failing, which is a different job and needs someone to look at your actual file.
Every template here is built the same way: inputs, calculations and output kept in separate sheets, no constants buried inside formulas, and a README tab explaining what to change. Each page shows the worksheet layout, the formulas that do the work and a worked example, so you can judge the fit before downloading.