#NUM!
a number is invalid or the result is impossible to represent.
what it means
The formula is well-formed and the arguments are numbers, but the maths cannot produce a valid result — an out-of-domain input, a value too large to represent, or an iterative calculation that never converges.
a formula that produces it
=SQRT(-1)common causes
- a domain error such as =SQRT(-1)
- a result too large or too small for the number range
- IRR/RATE-style iterative functions that fail to converge
- a negative or zero argument where the function requires a positive one
how to fix it
- validate the input range before calling, e.g. =IF(A1<0, "", SQRT(A1))
- supply a closer starting guess to an iterative function
- rescale the calculation so intermediate values stay representable