3 articles
Most amortization tables are a fragile ladder of copy-down formulas that shatter the moment you insert a row. Here's the classic PMT/IPMT/PPMT build that never chains off the row above, the Excel 365 spill that produces all 360 rows from one cell, and a free workbook that also prices what an overpayment actually buys you.
Excel's NPV function quietly assumes your first cash flow lands one full period in the future, so it discounts the whole project by an extra period and hands you a number that is 9% light. Here's the classic fix, the XNPV/XIRR way for real dates, and a free workbook that reproduces every answer from first principles.
VLOOKUP hands the whole amount one flat rate. Graduated commission, tax brackets and bulk pricing need marginal maths instead — here's the SUMPRODUCT one-liner that works in every Excel, the 365 MAP version that spills the whole column, and a free workbook that proves both against a hand-built calculation.