Long formulas look difficult because several operations are compressed into one line. The fastest way to understand them is not to read left-to-right like a sentence. Instead, identify the outer function, then work inward one argument at a time.
Start with the outer wrapper
In a formula such as =IFERROR(XLOOKUP(A2,Products!A:A,Products!D:D),"Not found"), IFERROR controls the final fallback while XLOOKUP performs the lookup. Knowing that hierarchy immediately separates error handling from the actual retrieval logic.
Mark the ranges and criteria
Cell references tell you where data comes from. Criteria such as quoted labels or comparison operators tell you how rows are selected. Write those pieces down in plain language before changing anything.
Test the inner function by itself
Temporarily remove wrappers such as IFERROR. If the inner lookup or calculation fails, hiding the error makes diagnosis harder.
Use names when formulas repeat concepts
LET can make complex formulas easier to audit because repeated values can be assigned descriptive names inside the formula.