Diagnose formula errors with symptoms and a five-step debugging routine.
Diagnose the cause before hiding the error
Check formula syntax and separators, inspect references, confirm input types, evaluate individual parts and verify the result with a known case. #N/A commonly means a missing lookup match; #DIV/0! requires a nonzero denominator; #SPILL! needs an empty output area. IFERROR should provide deliberate recovery rather than conceal incorrect calculations.