# XL: Formulas to Find the Log and Inverse Log of a Number

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##### Summary
Microsoft Excel has built-in functions to calculate the logarithm of anumber with a specified base, the logarithm with base 10, and the naturallogarithm. To calculate the inverse log of a number in the first twocases, raise the base to the power of the value returned by theparticular logarithm function being used. To find the inverse naturallog, use the EXP function.
You can use the formulas in the following table to perform logarithmic and inverse log operations:
`   Formula       Operation              Example            Result   ---------------------------------------------------------------------   =LOG(n,b)     Log base b of n        =LOG(8,2)          3   =(b)^(x)      Inverse log of the     =2^3               8                 number x, base b   =LOG10(n)     Log base 10 of n       =LOG10(100)        2   =10^(x)       Inverse log of the     =10^2              100                 number x, base 10   =LN(n)        Natural log of n       =LN(100)           4.6051702   =EXP(x)       Inverse natural        =EXP(4.6051702)    100                 log of the number x				`
In the preceding table, n is a variable that is either a value or the address of a cell containing a value, b (in the first function) is the base with which the logarithm is calculated, and x is a variable representing the result of the log function being used.

NOTE: Unless a different value or cell address is specified, thedefault value for the base is 10.
revlog log10 arc Anti AntiLog anti-log \* 5x XL2000 xl2002 xl2001 xl98 xl97 XL2003 XL2007 XL2010
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Article ID: 214116 - Last Review: 09/23/2015 06:46:00 - Revision: 6.0

Microsoft Excel 2000 Standard Edition, Microsoft Excel 2002 Standard Edition, Microsoft Excel 97 Standard Edition, Microsoft Excel 2001 for Mac, Microsoft Excel 98 for Macintosh, Microsoft Office Excel 2003, Microsoft Excel 2010, Microsoft Office Excel 2007, Excel 2016, Microsoft Excel 2013

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