upcCheckDigit ( upcString )

Calculates UPC code check digit for any length UPC code. NOTE: Requires FMP 18 or later

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Andrew Sasaki - Show more from this author

Sample input:

upcCheckDigit ( "72554-00192" )
upcCheckDigit ( "6927719811693" )

Sample output:

5
3

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

Let ( [ 
	/* filter non-digit characters */
	upcString = Filter ( upcString ; "0123456789" ) ; 
	/* determine number of iterations */
	charCount = Length ( upcString )  ; 
	/* loop thru characters, add them to the total */
	UPCsum = While ( [ iteration = 1 ; UPCtotal = 0 ] ;
		iteration < charCount + 1 ; 
		[ UPCdigit = GetAsNumber ( Middle ( upcString ; iteration ; 1 ) ) ; 
		/* odd characters - first, third, fifth, etc - get multiplied by 3 */
		UPCtotal = UPCtotal + If ( iteration/2 = Int ( iteration/2 ) ; UPCdigit ; UPCdigit * 3 ) ; 
		iteration = iteration + 1 ] ;
		UPCtotal ) ; 
	/* round up upc sum to nearest multiple of 10 */
	roundedTotal = Ceiling ( UPCsum / 10 ) * 10 ] ; 
	/* subtract the lower number from the higher one to get the check digit */
roundedTotal - UPCsum  )

Given a UPC code without a check digit, this will generate the check digit. The formula is:

* Sum of the odd digits - the first, third, fifth, etc. - multiplied by 3
* Sum of the even digits added to the first sum
* The difference between that number and the number rounded up top the nearest multiple of 10 is the check digit

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Note: these functions are not guaranteed or supported by BrianDunning.com. Please contact the individual developer with any questions or problems.

upcCheckDigit ( upcString )

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