Logarithm is different using VBA and Excel function

Question

I'm trying to get the log of a number but it looks like the Worksheet function gives one answer, and VBA another.

In VB, using Log(Range("A2")) where A2 is 7, I get 1.94591014905531, which is the correct answer. But, if in the worksheet, I use =Log(A2,10) or =Log10(a2), I get 0.84509804. What's going on here?

Possible duplicate of Simple recursive function in VBA with Excel not returning expected result — GSerg
– GSerg, Commented May 12, 2016 at 7:14

Michael S Priz · Accepted Answer · 2015-07-24 19:41:12Z

21

VBA's Log function is the natural log. If you want log base ten you will have to use the logarithmic identity for converting bases. Like so: Log(x)/Log(10).

answered Jul 24, 2015 at 19:41

Michael S Priz

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2 Comments

Mark Butler Over a year ago

Also, that you refer to 1.94593... as the correct answer implies that it is indeed the natural log you are looking for? To do this in a formula, use =LOG(A2,EXP(1)). Here, EXP(1) gives us e^1 = e = 2.72...., the base of the natural log.

Jacktose Over a year ago

You can also use Excel's version with Application.WorksheetFunction.Log(x).

fnome · Accepted Answer · 2017-12-15 21:16:12Z

0

Function roundit1(nn As Variant, sd As Variant)
    nn = Val(nn)
    If Not (nn = 0) Then
        xx = (1 + Int(Log(Abs(nn)) / Log(10)))
    Else
        xx = 0
    End If
    ' significant digits
    roundit = sd - xx
    If roundit < 0 Then roundit = 0
   roundit1 = Round(nn, roundit)
End Function

answered Dec 15, 2017 at 21:16

fnome

1

1 Comment

pirho Over a year ago

While this may answer the question, it is better to explain the essential parts of the answer and possibly what was the problem with OPs code.

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