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Math & Trig
The Excel LOG10 function returns the base-10 logarithm of a number — the common logarithm used in pH, decibel, and order-of-magnitude calculations.
Quick answer:
=LOG10(1000) log base 10 of 1000 = 3
Syntax
=LOG10(number)
| Argument | Description | |
|---|---|---|
number | Required | The positive real number whose base-10 logarithm you want. Must be greater than zero. |
How to use it
LOG10 answers “10 to what power gives this number?”:
=LOG10(1000) // 10^3 so = 3
=LOG10(100) // = 2
=LOG10(1) // = 0
It is identical to LOG(number) with the base left off — LOG10 just makes the intent explicit. For base e use LN, and for any other base use LOG(number, base).
Positive numbers only. LOG10 of zero or a negative number returns a #NUM! error, since the common log is undefined there.
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Live demo
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Result:
Practice workbook
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Frequently asked questions
Is LOG10 the same as LOG without a base?
Yes.
=LOG10(1000) and =LOG(1000) both return 3, since LOG defaults to base 10. LOG10 just states the intent.What is the base-10 log of 1000?
=LOG10(1000) = 3, because 10 raised to the power 3 equals 1000.When is the common (base-10) logarithm used?
In pH chemistry, decibel sound levels, the Richter scale, and any ‘orders of magnitude’ calculation.
Why does LOG10 return an error for some inputs?
The argument is zero or negative. The base-10 logarithm is only defined for positive numbers, so those return a #NUM! error.
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