INVSUMINV Function (Gnumeric)

• Introduced: Gnumeric 1.3.2 release notes explicitly record this function being added.
• Supported in: Gnumeric 1.12.62, with no retirement established.
• Scope: Desktop Gnumeric with the Engineering plugin; English comma-separated formulas are shown.
• Checked: October 14, 2026. Reference and boundary tables plus the explicit advanced-check formula were recalculated through 1.12.57 ssconvert. Current 1.12.62 source was inspected; that later release was not executed.

INVSUMINV returns 1/(1/x1+1/x2+…), for the collected positive values. This is the reciprocal of a sum of reciprocals, not the arithmetic mean and not automatically the harmonic mean. A collected zero makes the result zero unless an invalid negative value causes an error. Versioned function help.

=INVSUMINV(x1[,x2,...])

The function accepts a variable list of arguments and ranges. At least one numeric value must remain after collection. Its collector ignores strings, Boolean values and blank cells. Negative collected numbers are invalid. The range routine separately checks zero rather than trying to divide by it. Brackets mark optional arguments; do not type the brackets into a formula. Function implementation.

Ordinary results are rounded to twelve decimal places; tiny nonzero values use scientific notation. The eight reference rows were independently checked.

For two ideal parallel resistances 2000 and 2000 in the same unit, =INVSUMINV(2000,2000) gives 1000. For 100 and 300 it gives 75. These are applications of the reciprocal-sum relation; the worksheet does not establish whether a physical circuit actually satisfies the ideal model.

If values are in B2:B3, =INVSUMINV(B2:B3) is a reproducible range form. Check that both cells are genuinely numeric. A text value can be ignored and leave a plausible-looking but incomplete calculation.

For n positive observations, the harmonic mean is n×INVSUMINV(values). With four values all equal to 4, INVSUMINV is 1, while the executed expression =4*INVSUMINV(4,4,4,4) returns 4. Confusing the reciprocal sum with the harmonic mean introduces a factor-of-n error.

For positive 2,3 and 6, the reciprocals add to 1, so the result is 1. The result cannot exceed the smallest positive member when at least one other positive member is included. Use that bound as a quick check on units and transcription.

The shown literal string “abc”, Boolean TRUE and empty F5 were all ignored when paired with numeric 2, leaving result 2. An all-text list and an empty argument list produced #VALUE!. Ignoring an entry is not the same as validating it.

The tested =INVSUMINV(0,-1) returned #VALUE!, so a zero does not override an invalid negative number. If zero represents a missing value rather than a physical zero, validate it before calculation. Extremely small positive inputs can overflow their reciprocals; the modest examples do not prove stable results for every numerical scale.

F5 below is an actually empty cell. The listed errors are native error results, not mathematical zeroes.

• Worksheet entry
• Numeric or argument-handling source

The retained workbook results include a deliberately stale SUM cache and an uncached SUM formula, both recalculated correctly. Native evidence covers the named 1.12.57 build and listed cases; cell-reference layouts and other explanatory compositions are instructions or independent mathematical checks unless explicitly identified as executed. Other locales, direct GUI entry and later-release output were not tested.