LN returns the natural logarithm of a positive number: it asks which power of e produces that value. For example =LN(1) is expected to return 0, and =LN(2) is expected to return approximately 0.693147181. These are mathematical expectations verified independently of the application; the values were not observed in a Calligra test.

=LN(x)

x (required) is a numeric argument or cell reference. The function returns a floating-point value. The real-valued natural logarithm is defined for x > 0. There is no optional base parameter: LN is always base e. For other bases, Calligra’s handbook separately documents LOG (base 10), LOG10, LOG2 and LOGN. It shows the unusual example LN(0) equals -inf; this is documentation, not proof of how an installed version exposes zero or negative inputs. Never silently rely on -inf or a particular spreadsheet error code in a portable workbook.

Evidence and scope: The official KDE function handbook and the source registry pinned to Calligra 26.08.2 (released 2026-10-08) were consulted on 2026-10-11. The registry confirms inclusion in the shipped source module, not that every operating-system package has the same functions enabled. KDE’s Calligra Sheets release page currently lists 26.08.2. The main documented installation environment is Linux, using a distribution package or Flatpak; Windows availability was not established for this review. These examples have not been entered or run in a native Calligra Sheets application.

Formula-entry conventions: Start a cell formula with =. Calligra’s English handbook writes multiple parameters with semicolons, as in IF(test;true_value;false_value); none of this function’s own calls takes multiple arguments except where explicitly shown in a composite formula. Locale-dependent decimal symbols and formula separators can differ: confirm them in the installed Insert → Function interface. Numeric constants in tables below use a decimal point for the English-locale example.

Create a new sheet with A1:C1 as shown; enter the five positive numeric values in B2:B6. In C2 type =LN(B2) and copy down through C6.

The expected values are rounded to six decimals; the underlying mathematical values have more digits. A negative result from LN(0.5) is entirely normal, even though the input must be positive.

Steps: Fill B2:B6 exactly, enter =LN(B2) in C2, and copy/fill to C6. If you type 0.5 using a decimal comma in your locale, use your installed application’s numeric convention instead of copying punctuation blindly. Explain to reviewers that C4 is about 2.302585 because e^2.302585 is about 10.

If a starting quantity grows from 1000 to 1210 over two years, the continuous annual rate is LN(final/initial)/years:

Enter in H2:

=LN(F2/E2)/G2

Expected H2 ≈ 0.095310180, or approximately 9.531018% after percentage formatting. This is not the same as an ordinary discrete CAGR calculation, =(F2/E2)^(1/G2)-1, whose expected answer is 10%. Both models can describe growth, but they answer different questions. Do not substitute the continuous rate for the discrete rate without specifying the model.

Guard against zero and nonpositive inputs

For a positive B2, the following formula returns its natural logarithm; otherwise it displays a clear input warning:

=IF(B2>0;LN(B2);"Enter a positive number")

The expected warning appears for B2=0 or B2=-2. This guard is a proposed worksheet design (not a reported runtime behavior), using the documented IF function. If F2 or E2 are zero/nonpositive in the advanced ratio, validate both quantities and G2 before relying on the result.

• Entering a zero or negative input: In real arithmetic LN is undefined at zero and for negative real numbers. The older KDE handbook says LN(0) is -inf; that statement is not an observed runtime result. Excel typically reports a numerical error instead. Avoid relying on either representation across versions.
• Confusing a negative output with an error: The logarithm of any input strictly between zero and one is negative; this is correct.
• Confusing LN and LOG: Calligra’s LOG is base 10, whereas LN is base e. LN(10) is about 2.302585, not 1.
• Wrong growth-rate model: Continuous annual growth uses LN of a ratio divided by years; discrete CAGR is a power formula.
• Imported text values: Test the numeric input and decimal formatting if results appear invalid. Do not assume a text string will be converted consistently.
• Error messages, infinities or cell-width problems: Check the argument domain, formula syntax, parentheses and cell formatting; the precise display is version/platform dependent and untested here.

Microsoft Excel’s LN function reference requires a positive real number and describes the inverse relation to EXP. LibreOffice Calc also provides a natural-log function. All use base e, but error handling at zero (the KDE handbook’s -inf example versus Excel’s numerical-error semantics), localized decimal marks and formula argument punctuation can differ. For portability, explicitly guard invalid inputs and avoid using any app-specific sentinel such as infinity to indicate missing data.

• Official KDE LN function: syntax and documented zero-input example, checked 2026-10-11.
• Pinned Calligra 26.08.2 math function registration, source-only support proof.
• Current KDE Calligra Sheets release information shows 26.08.2 dated 2026-10-08, accessed 2026-10-11.
• Microsoft Excel LN reference, LibreOffice mathematical-functions manual; comparisons checked 2026-10-11.

• Calligra Sheets — function documentation
• KDE function handbook
• LibreOffice Calc
• Pinned Calligra 26.08.2 math function registration

Verification status: Official documentation checked; example outcomes were independently reasoned or arithmetically checked where applicable. Not executed in Calligra Sheets.

• No genuine Calligra Sheets screenshots are included; this guide does not use mock application images.