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Source Code for Master Lock Combination Calculator

Code to calculate possible combinations for a Master combination lock given the last number in the combination. This source is in PHP.

<table summary="Possible Master Lock Combinations">
<caption>Possible Combinations</caption>

$default_c3 = 0;
$c3 = (int) isset($_GET["last_comb"])? $_GET["last_comb"] : $default_c3;
if ($c3<0 || $c3>39) $c3 = $default_c3;

for ($c2=($c3+2)%4; $c2<40; $c2+=4)
	print "<tr>";
	for ($c1=$c3%4; $c1<40; $c1+=4)
		if ($c1-$c2==2 or $c1-$c2==6 or $c2-$c1==38 or $c2-$c1==34 or abs($c3-$c2)%36==2)
			echo "<td> </td>";
			echo "<td>$c1 - $c2 - $c3</td>";
	print "</tr>\r\n";


11 Responses to “Source Code for Master Lock Combination Calculator”

  1. So nice to have it online. I have the Excel file if anyone wants it?

    Posted by Dan Casta | July 8, 2012, 5:21 AM
  2. Help! I have a Master Lock and forgot the combo! Serial Number 8000148

    Posted by Jennifer | October 20, 2011, 8:24 AM
  3. I’m iprmeessd! You’ve managed the almost impossible.

    Posted by Lorena | April 16, 2011, 8:16 AM
  4. How did you find this formula for master locks?

    Posted by Rob | November 14, 2010, 11:39 PM
    • It was based on the physical limitations of the lock. One such limitation was the mechanical resolution was 1 or 2 numbers away from the published combination. So, if the published combo was 4-32-16, for example, 5-32-16 would work as well. Some may describe this as sloppiness in the lock mechanics.

      Posted by Mike | January 26, 2011, 11:52 PM
  5. What about for a combination lock with numbers from 0 to 49?

    Posted by matt | June 19, 2010, 8:22 PM
  6. Can you make it so that I can run this program on your website? I don’t have php on my computer. This would be an excellent utility for they iPhone.

    Posted by TJ Mathews | September 27, 2009, 3:12 PM

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