LOG10 calculates the common (base-10) logarithm of a positive numeric input: =LOG10(100) has the expected result 2. It uses an unambiguous fixed base and one required argument, which helps make cross-program log formulas easier to audit.

=LOG10(x)

• x (required): one positive numeric value or a cell reference containing a positive number. KDE’s parameter description requires positive floating-point input.
• Base and defaults: the base is 10; no base parameter and no optional argument is documented for this function.
• Return: floating-point logarithm. The result is zero at x = 1, positive above one and negative for a positive fraction below one.
• Documented edge case: KDE says LOG10(0) is an error; the exact application’s error message was not observed.

This guide is release-scoped to Calligra Sheets 26.08.2 (KDE’s release listing dated 2026-10-08). The function is present both in the official stable-KF6 function handbook and in KDE’s pinned 26.08.2 source-function registry; references were accessed 2026-10-11. The handbook’s surrounding revision may be older than the release: source registration documents that a name is available in that release’s code, not that it was executed or enabled in a particular Linux package or other platform. Calligra recommends Linux packages/Flatpak; installed versions and optional components can differ.

In a cell, start a formula with =. The KDE English documentation uses semicolon (;) as the multiple-argument separator; the examples use periods for decimal points. Actual entry conventions may vary with locale or build. Use the installed function selector to confirm locally and keep input columns numeric, not numeric-looking text. Results are floating-point values; displayed precision is controlled by cell formatting. All results below are expected mathematical values, not observed Calligra 26.08.2 outputs.

1. Enter Positive numeric ratio in A1 and Base-10 exponent in B1.
2. Fill A2:A6 with the values below, entering the values as numbers rather than quoted strings.
3. In B2 enter =LOG10(A2) and fill through B6.
4. Display five decimal places if you want to compare non-powers-of-ten; the results are not percentages.

Change A3 to 0.1: −1 is the mathematically expected result, not an error. The input must be positive; an output may be negative.

The simplified absorbance relationship is A = log₁₀(I₀/I), where I₀ is the reference light intensity and I is the transmitted light intensity. Both must be positive and in identical intensity units. This is a standard mathematical model; it is not a substitute for instrument calibration or a laboratory protocol.

• In D1 put Reference intensity, E1 Transmitted intensity, and F1 Absorbance (calculated).
• Put 100 in D2 and 10 in E2. In F2 enter =LOG10(D2/E2); expected 1.00000.
• Put 100 in D3 and 1 in E3. In F3 use the same expression for row 3; expected 2.00000.
• Put 100 in D4 and 50 in E4. F4’s expected result is approximately 0.30103.
• To produce an editorial warning rather than divide by zero, use =IF(AND(D2>0;E2>0);LOG10(D2/E2);"Check intensities"), provided the inputs are numeric. IF and AND are documented separately; this is a proposed, unexecuted Calligra formula.

If the ratio is below one, the logarithm is negative, which could indicate a swapped reference/sample or other experiment-specific issue. Check physical assumptions before interpreting it.

• LOG10(0): the KDE handbook explicitly says it produces an error. The precise error display has not been verified on 26.08.2.
• Negative input: no finite real common logarithm; correct sign, reference and intermediate ratio first.
• Numerator or denominator zero: in the absorbance example, both intensities must be positive; the division itself can fail before the logarithm.
• LOG10 versus LOG: Calligra documents both as base 10, but LOG10 states the base in the function name. Neither documented Calligra form accepts a second argument.
• LN confusion: natural logs use base e and produce different numbers; LN(10) is not 1.
• Rounding and imports: LOG10(2) is approximately 0.301029996, so a 5-decimal display shows 0.30103. Pasted text, locale separators and precision formats may alter apparent results without changing the formula definition.
• Different error codes: documentation supports the mathematical domain and the explicit zero error, not exact UI codes for every malformed input.

Excel and LibreOffice Calc both document LOG10(number) with a single numeric argument, making the function easier to transfer conceptually than a custom-base formula. Calligra’s base-10 LOG(x) is another mathematical equivalent. By contrast, both Excel and Calc document LOG(number,[base])-style expressions with a possible second argument, whereas Calligra requires LOGN(value;base) when a non-10 base is desired. Locale separators, text coercion, error rendering and precision still require testing before distributing imported spreadsheets.

• Calligra Sheets — function documentation
• official stable-KF6 function handbook
• KDE Calligra 26.08.2 source registration
• LibreOffice Calc mathematical functions

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.