GAMMAINV Function (Calligra Sheets)

• Introduced: First release not established; the name is present in Calligra 2.4.0 source.
• Supported in: Calligra Sheets 26.08.2, with no retirement established.
• Scope: Desktop Sheets with the Statistical module. Examples use English semicolon-separated formulas.
• Checked: October 14, 2026. Selected formulas ran through the official 25.04.2 engine library. Source and independent mathematics were checked. This is engine evidence, with no GUI-cell or import verification; 26.08.2 was source-checked only.

GAMMAINV finds x such that the gamma cumulative probability P(X≤x) equals the supplied probability. It uses shape α and scale β, not a rate parameter. A gamma variable with this parameterization has mean αβ and variance αβ². Function help.

=GAMMAINV(probability;shape;scale)

All three arguments are required. For a valid distribution, shape and scale must be positive and 0≤probability<1. The wrapper rejects negative shape or scale but omits the equality check; the boundary table preserves that discrepancy. Registration and implementation.

The engine and mathematical columns are separate. Results are rounded to twelve decimal places, or thirteen significant digits in scientific notation for very small or large values. This is a display choice, not an accuracy guarantee. NaN and infinity are nonfinite outputs; an engine error flag is checked separately from those values.

For a gamma model with shape 2 and scale 2, the 90th-percentile cutoff is approximately 7.779440339735 mathematically. The engine returns its nearby approximation shown in the table. About 90% of the modeled observations fall at or below that cutoff; it is not a 90% chance of observing exactly the cutoff.

If another source uses rate λ, convert to scale β=1/λ before supplying the third argument. For rate 0.5, use scale 2. Using 0.5 directly would describe a different distribution.

With shape 1, the gamma model becomes exponential, and the inverse has the independent formula x=−β ln(1−p). At p=0.5 and β=1 this is ln(2), approximately 0.693147180560. The retained engine result differs in later digits because its inversion uses the application’s approximate CDF.

The roundtrip below checks the application against itself at p=0.9. A successful roundtrip is useful but cannot establish independent quantile accuracy: two related approximations may agree. Both the independent references and the engine values are retained.

The executed advanced check was:

=GAMMADIST(GAMMAINV(.9;2;2);2;2;1)

Its engine result was 0.9.

Probability zero returns zero; probability one is rejected rather than reported as an infinite quantile. Text “abc” was converted to a zero probability in the selected engine call. A plausible zero therefore does not prove that input data was valid. The iterator has finite iteration limits and can return #VALUE! on nonconvergence. The displayed decimal places are not a general accuracy guarantee.

• Function-specific implementation
• Versioned function help
• Inverse helper
• Gamma Dist helper
• Conversion helper

The statistical module and value-calculation helpers are byte-identical between the inspected 25.04.2 and 26.08.2 sources. That comparison supports the source discussion but does not establish later-version native output, every locale or arbitrary extreme-parameter accuracy.

GAMMADIST.