Change 18-digit dec number to hex

[Toria]

Hello,

When I have this number, 268435457800737937, Excel gives me an error when I
do the DEC2HEX formula. In an online converter, I get 3B9ACA06B551480. Any
ideas why I can't get a response from Excel?

 

[Shane Devenshire]

Hi,

First problem is that there are no 18 digit numbers in Excel. Excel support
15 digits.

 

[Toria]

Thanks, Shane! Just to confirm, there's no way in Excel to convert to hex
from an 18-digit dec...?

 

[Gord Dibben]

If you take a look at help on dec2hex you may find the source of your error.

If number < -549,755,813,888 or if number > 549,755,813,887, DEC2HEX returns
the #NUM! error value.

Your example number certainly exceeds the maximum.

In help you will find other sources for errors arising.


Gord Dibben MS Excel MVP

 

[David Biddulph]

Did you read Excel Help for DEC2HEX?
"If number < -549,755,813,888 or if number > 549,755,813,887, DEC2HEX
returns the #NUM! error value."

Remember also that Excel numbers are stored to a precision of 15 significant
figures.

If you have your 18 digits as a string in A1 you can get an *approximation*
to the result by breaking it up, such as
=DEC2HEX(A1/2^32)&DEC2HEX(MOD(--A1,2^32))
That gives 3B9ACA06B5510E0

If you convert it back, again breaking it up to manageable chunks,
=HEX2DEC(LEFT(A2,LEN(A2)-8))*2^32+HEX2DEC(RIGHT(A2,8))
gives 268435457800737000

If you look at your result, you will realise that 3B9ACA06B551480 cannot be
an accurate answer, as with zero at the end it must be a multiple of 16,
which 268435457800737937 isn't.

Doubtless with a more complicated segmentation of the text strings, you
could get the correct answer. For what it's worth, the Windows calculator
gives 3B9ACA06B551491

 

[Rick Rothstein]

If you are up for a UDF (User Defined Function), then give the function
below a try. To install it, press Alt+F11 to get into the Visual Basic
Editor, then click Insert/Module on its menu bar and copy/paste the function
below into the code window that opened up. Then you can use the function
just like a built-in function. Making sure your large number are entered as
text (either format the cell as text before entering the number into it or
place an apostrophe in front of the number when you enter it); for example,
put '268435457800737937 in A1) and then put...

=BigDec2Hex(A1)

in the cell you want the Hex value to be place in. Here is the function...

Function BigDec2Hex(ByVal DecimalIn As Variant) As String
Dim X As Integer
Dim BinaryString As String
Const BinValues = "*0000*0001*0010*0011" & _
"*0100*0101*0110*0111" & _
"*1000*1001*1010*1011" & _
"*1100*1101*1110*1111*"
Const HexValues = "0123456789ABCDEF"
Const MaxNumOfBits As Long = 96
BinaryString = ""
DecimalIn = Int(CDec(DecimalIn))
Do While DecimalIn <> 0
BinaryString = Trim$(Str$(DecimalIn - 2 * _
Int(DecimalIn / 2))) & BinaryString
DecimalIn = Int(DecimalIn / 2)
Loop
BinaryString = String$((4 - Len(BinaryString) _
Mod 4) Mod 4, "0") & BinaryString
For X = 1 To Len(BinaryString) - 3 Step 4
BigDec2Hex = BigDec2Hex & Mid$(HexValues, _
(4 + InStr(BinValues, "*" & _
Mid$(BinaryString, X, 4) & "*")) \ 5, 1)
Next
End Function

Note that for your example number, the function returns 3B9ACA06B551491
which is the correct answer (not the answer you showed in your posting).

 

[David Biddulph]

I said below:
"Doubtless with a more complicated segmentation of the text strings, you
could get the correct answer."

One possibility which seems to work is
=DEC2HEX(A1/2^32)&DEC2HEX(MOD(INT(A1/10000),2^32)*10000+RIGHT(A1,4))

 

[Rick Rothstein]

Just to point out... the function I posted will work with any decimal number
(entered as a text value) up to 28 decimal digits long. Actually, it will
work for some, but not all 29 digit decimal numbers; but if you stick to 28
or less, you can handle their entire range of values.

 

[Rick Rothstein]

I get a #NUM! error for a value of '123456789012345678 with your formula.

 

[David Biddulph]

True. It obviously needs someone with a clever UDF then, Rick.

 

[Toria]

Thank you to all who responded. This helps immensely!