#CALC!
The calculation engine cannot produce the requested array.
What it means
The formula is valid but asks for something the array engine cannot represent, most often an empty array, or an array nested inside another array.
How to fix it
- Give the filter an if-empty argument.
- Flatten the calculation so it returns one array, not nested ones.
- Compute the intermediate step in its own cell.
Common causes
- A filter that matched nothing and has no fallback.
- A formula that would produce an array of arrays.
- An array operation the engine does not support.