LOG
Return the logarithm of a number to a given base, or to base 10 when no base is given.
Syntax
LOG(number, [base])| Argument | Required | Description |
|---|---|---|
number | Required | A positive number. |
base | Optional | The base of the logarithm. Defaults to 10. |
Examples
Every example below was executed against VisiGrid engine 0.54.0 — not
transcribed from another vendor's documentation. Reproduce any of them with vgrid calc.
| Formula | Result | Notes |
|---|---|---|
=LOG(100) | 2 | With no base, LOG is base 10. |
=LOG(8,2) | 3 | Two cubed is eight. |
=LOG(1024,2) | 10 | How many times 1,024 halves before it reaches 1. |
=LOG(0) | #NUM! | |
=LOG(10,1) | #NUM! | Base 1 is not a usable base. |
The default base is 10
LOG(x) is base 10, matching Excel and Sheets. That catches out anyone coming
from a programming language, where log(x) usually means the natural log. For
base e use LN.
”How many times” questions
A logarithm answers how many times you multiply by the base to reach a number. Base 2 counts halvings and doublings:
=LOG(1024,2) → 10— ten rounds of a knockout tournament for 1,024 entrants, or ten binary-search steps through 1,024 sorted rows.
Errors
Zero and negative numbers have no logarithm, so they return #NUM!. So does a
base of 1, and so does a zero or negative base. If a column feeding LOG can
contain zeros, test for them before taking the log rather than after.
Excel compatibility
Matches Excel, including the default base of 10.