LOG
Math & Trig
Returns the logarithm of a number to a specified base.
Translations
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Syntax
LOG(number, [base])Arguments
numberPositive numberbaseBase of logarithm (default 10)(optional)
Examples
=LOG(100)2
Log base 10 of 100
=LOG(8,2)3
Log base 2 of 8
=LOG(A1,E)Natural log
Same as LN
Tips & Best Practices
- •Default base is 10
- •Use LN for natural logarithm
- •Number must be positive
Common Mistakes
- •Forgetting that LOG's second argument (base) defaults to 10 if omitted, so LOG(100) returns 2 (log base 10), which surprises anyone expecting a natural logarithm
- •Applying LOG to zero or a negative number, which returns a #NUM! error since logarithms are only defined for positive numbers
- •Confusing LOG with LOG10 or LN - LOG is flexible with any base, LOG10 is fixed to base 10, and LN is fixed to base e, and picking the wrong one for a specific need is an easy mix-up
Related Functions
Frequently Asked Questions
What base does LOG use if I don't specify one?
Base 10 by default - LOG(100) without a second argument returns 2, the same as LOG10(100).
Why does LOG return #NUM!?
The input number is zero or negative - logarithms are only defined for positive numbers in real-number math.
What's the difference between LOG and LN?
LOG lets you specify any base (defaulting to 10), while LN is fixed specifically to the natural logarithm, base e - LN(x) is equivalent to LOG(x, EXP(1)).
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