LOG Function in Google Sheets: Examples, Pitfalls & Compatibility
LOG in Google Sheets: calculate a logarithm in an explicit base, with base 10 used when omitted. Includes worked examples and application-specific cautions.
Verification status: Official documentation referenced; example outcomes independently reasoned or arithmetically checked where stated. Not executed in Google Sheets. How formula examples are checked
Quick answer: Use LOG in Google Sheets to calculate a logarithm in an explicit base, with base 10 used when omitted. The official LOG reference is the source for the function definition and platform-specific rules described below.
Syntax and arguments
=LOG(value, [base])
value (required): A strictly positive real value.
base (optional): The logarithm base; the documented default is 10. For a real logarithm use a positive base other than 1.
Square brackets mark optional arguments; do not type those brackets into the example formulas. Examples use English function names, comma argument separators and decimal points. Adapt formula separators to your workbook settings, not punctuation inside quoted text.
When to use it
Use LOG when a problem names a base, such as the number of repeated doublings. The result is the exponent needed to produce the input from that base. Do not assume that LOG means the natural logarithm in a spreadsheet.
Three worked examples
Each example is independent. Where input cells are listed, enter those values first; otherwise the formula is self-contained. Expected outputs are independently checked calculations or documented error expectations, not captured results from Google Sheets.
Example 1: Find an exponent in base three
=LOG(81,3)
Expected result: 4.
Three to the fourth power is 81.
Example 2: Check omitted-base behavior
=LOG(10000)
Expected result: 4.
The default base is 10, matching the detailed Google help.
Example 3: Use a positive base below one
=LOG(8,0.5)
Expected result: -3.
One half raised to -3 is 8. The base is positive and is not 1, so the mathematical logarithm is defined.
Put it to work safely
Write the chosen base explicitly in reusable formulas so readers do not need to remember the default. Verify the result by raising the same base to the returned exponent. Use simple exact-power inputs as baseline tests before working with measured values or interpreting a noninteger logarithm as a whole count of stages.
Common mistakes and fixes
The answer seems to use the wrong base. An omitted base defaults to 10. Supply the base or use LN for the natural logarithm.
A base of one is entered. Every real power of one is one, so this does not define an ordinary inverse logarithm. Validate the base.
A negative logarithm is labelled an error. The output may be negative for a valid positive input or a valid base below one. Inspect the mathematical rule, not only the sign.
Google Sheets-specific notes
Google’s detailed LOG help says that the base is optional and defaults to 10, even though the condensed catalogue syntax may not display optional brackets. This guide follows the detailed argument explanation rather than inferring that omission is invalid. See the vendor reference for the current definition.
Excel and Google Sheets comparison
Both detailed references use base 10 by default. A base below one is mathematically valid, but precision and exceptional cases need a native check when the result drives a critical workflow.
Compare the LOG guide for Microsoft Excel and its official documentation. Having a guide in both libraries establishes two documented references, not a certificate of identical behavior across releases, locales or file conversions.
Related guides
LN, LOG10, POWER, ROUND · All Google Sheets functions.
Evidence and testing scope
Editorial verification: Official references retrieved on 2026-10-12. The three worked cases are included in this release’s reproducible Python checking suite. It checks the stated arithmetic, calendar or text model and the expected documented error classification; it is not the Google Sheets calculation engine. No native application run, UI screenshot, maximum-size benchmark or cross-version certification is claimed. Review the editorial testing standards before relying on a formula in a critical workbook.