Apple iWork '09 - Manual (Page 180)

Example
=LN(2.71828) returns approximately 1, the power to which e must be raised to produce 2.71828.
Related Topics
For related functions and additional information, see:
“EXP” on page 174
“LOG” on page 180
“LOGINV” on page 268
“LOGNORMDIST” on page 269
“Listing of Numeric Functions” on page 167
“Value Types” on page 36
“The Elements of Formulas” on page 15
“Using the Keyboard and Mouse to Create and Edit Formulas” on page 26
“Pasting from Examples in Help” on page 41
LOG
The LOG function returns the logarithm of a number using a specified base.
LOG(pos-num, base)
 pos-num: A positive number. pos-num is a number value and must be greater than 0.
 base: An optional value specifying the base of the logarithm. base is a number
value and must be greater than 0. If base is 1, a division by zero will result and the
function will return an error. If base is omitted, it is assumed to be 10.
Examples
=LOG(8, 2) returns 3.
=LOG(100, 10) and LOG(100) both return 2.
=LOG(5.0625, 1.5) returns 4.
Related Topics
For related functions and additional information, see:
“LOG10” on page 181
“Listing of Numeric Functions” on page 167
180 Chapter 8 Numeric Functions