PlanMaker #NUM!: Check What the Formula Can Accept

Scope: FreeOffice PlanMaker 2024 desktop, English official manual checked October 21, 2026. Translated labels may differ. No PlanMaker execution or screenshot was performed. Expected results combine documented error rules with independently checked arithmetic; they are not native test observations. Use a disposable workbook.

Separate numeric type from permitted value

A value can be numeric and still be outside a function’s allowed range. The FreeOffice 2024 error reference documents #NUM! for that situation and specifically gives a negative argument to SQRT as an example. This is not the same diagnosis as text where a number was required.

Read the input expression independently of the outer function. In a subtraction followed by a square root, inspect the subtraction before modifying the square-root calculation.

A controlled domain test

In a disposable workbook enter 36 in A2 and 45 in B2. Enter =A2-B2 in C2 and =SQRT(C2) in D2. The independently calculated C2 value is -9. The documented negative-input rule predicts #NUM! in D2.

For this example, the documented model was supposed to calculate the square root of the second amount minus the first. Correct C2 to =B2-A2. C2 should be 9 and D2 3, because 3 × 3 = 9.

Change B2 to 36. The difference and square root should both be 0. Change B2 to 100. C2 should be 64 and D2 8. Finally, restore B2 to a value below 36: the invalid-domain condition should return. The direction change is justified only by this exercise’s stated model.

Do not repair the symptom by changing the question

Taking an absolute value would make a negative input positive, but would also change the model. Reversing every subtraction or replacing negative values with zero has the same problem. Verify source units, reference order and the intended domain before choosing a correction.

If negative differences are legitimate inputs, the real-valued square-root model may be inappropriate. Retain the exception and review the mathematical requirement rather than silently converting the quantity. A later calculation that accepts complex values would be a different, explicitly documented model.

This page does not claim every #NUM! has the same cause. Consult the particular function’s argument restrictions for other cases. The site’s SQRT reference gives additional examples but is scoped to PlanMaker 2026; it is not evidence of every paid/free feature being interchangeable. The negative-input diagnosis here is supported directly by the FreeOffice 2024 manual, and no paid tracing feature is needed.

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