If a workbook calculation uses LAMBDA and shows #CALC! or #VALUE!, check how the function is called before changing the calculation itself. An uncalled LAMBDA in a cell produces #CALC!; the wrong number of supplied arguments produces #VALUE!. These are two specific causes, not explanations for every occurrence of those errors.

This guide is for people maintaining reusable formulas in Excel for Microsoft 365 or Excel 2024. Work in a saved copy of the workbook. If you only need to enter data into someone else's report, give its owner the affected cell and error instead of changing shared function definitions.

Separate the definition from the call

The formula =LAMBDA(length,width,length*width) defines a calculation with two inputs. In a worksheet cell, append the input values to run it: =LAMBDA(length,width,length*width)(3,4). This returns 12. A call with only one input does not match this definition.

For your own formula, compare the number and order of supplied values with its declared parameters. Then check the underlying calculation using an input with a known answer. A result without an error can still use the wrong units or business rule.

Check the workbook name

In Excel for Windows, use Formulas → Name Manager. For an existing named function, inspect its definition and scope before editing it; other cells may depend on that name. When creating a new function, choose an unused descriptive name and Workbook scope. In Refers To, store the LAMBDA definition without the sample call.

For example, a name such as AreaFromSides referring to the definition above is called as =AreaFromSides(3,4). Compare the direct and named calls before using the repaired definition in the report. Recheck the affected totals against known inputs, including any permitted boundary values.

Source: Microsoft: LAMBDA function.