Introduction: How to Crack a Masterlock Padlock.

Picture of How to Crack a Masterlock Padlock.

This little instructable will demonstrate how to narrow down the possible combinations for your lock from over 60,000 to 80. This is good for if you lose "your" combination.

Step 1: Knowing Thy Lock.

Picture of Knowing Thy Lock.

Before you find your numbers, you must know a few things about your lock.

First of all, there is a dial, a body, and a clasp (The U shaped thing on the top that comes out when unlocked).

When you open your lock you would normally spin the dial right a few times to reset, then go to your first number. Then, you would turn left, passing your first number once, then stopping on your second number. Finally, you would turn right again to your third, and final number and pull on clasp.

Okay, now you know thy lock.

Step 2: Finding Your Third Number

First, you must find your 3rd number of 3. To do this, turn right a few times to reset, then go to 0 on the dial. pull hard on the clasp and turn left a little until you notice your dial only turns within a little space. Now, you will need to use your brain cells to figure out the number in the middle. For instance, if the dial were stuck between 3 and 4, the number would be 3.5. Once you have your middle number written down, release the clasp, and turn left one number and pull again and turn more until you are stuck in another groove. Write down the number in the middle of the space. Repeat this process until you get 12 numbers. Not 8; 12. Okay? Your list might look like this:


So what you do, is take your pencil and cross out all the numbers with decimals (.5, .25, .75)
now you should have 5 numbers. If not, you didn't use enough brain cells to get the right middle number. Try again. But if you do have 5, you will notice 4 of the 5 end in the same number. Cross these out to. That should leave one number. In the case of the list above, that number would be 19.
That final-left number, is your third number.

Step 3: Finding Your First Number.

Okay. Now that you have you third number, it's time to get your first. Take your third number and divide it by four. Take the remainder. In our example our 3rd is 19 so we divide by 4 and keep the remainder. In this case, it would be 3. Hard? No. Now take your remainder ( Either 0,1,2, or 3) and write it down. now add 4. now write that down. Now add 4 to That new number. wright it down. Keep doing this pattern until you have 10 numbers down. Now stop. These are all the possible first numbers. Hooray!

19/4 = 4 R3(remainder)
3 + 4 = 7
7 + 4 = 11

3,7,11,15,19,23,27,31,35, and 39

Step 4: Finding Your Second Number.

Mmmkay. Now think way back 5 minutes ago and try to remember that little remainder. If its a 0 or a 1, add 2 , if its a 2 or a 3 subtract two. Now add 4. Write down. Do that 9 more times. Good job. Now take away any numbers +/- 2 from your third number. Now you have all the possible numbers for your second number.

Remainder = 3
3 - 2 = 1
1,5,9,13,25,29,33, and 37

Step 5: Narrowing It Down Even More.

Okay. Now you should have 10 1st numbers, 10 2nd numbers, and 1 third number.
Now remove any 2nd numbers +/- 2 from your third. Wallah! you know have narrowed it down by 20 poss. combinations.

Step 6: Finding the Right One

Now take your numbers and make a table and try out all the diff combos and cross them off if they don't work, so you can remember.
P.S. This may not work on older models and ones with locks in back.(Haven't tried any of those yet)


AlexisM97 (author)2017-03-13

I have a problem, I only have four whole numbers for the first few steps. (2.5, 6, 9.5, 12.5, 16, 19.5, 22.5, 26, 29.5, 32.5, 36, and 39.5) I have done and redone the process multiple times and have gotten the same result every time. How do I find my third combination number?

andrewc283 (author)2016-08-02

I know that my third # is 20 cuz the last five # were 6, 16, 20, 26, and 36. I got 10 1st #s 0,4,8,12,16,20,24,28,32, and 36. I got 10 2nd #s 2,6,10,14,18,22,26,30,34,and 38.
How do i make twenty combinations left. I dont get the next step.

Bushhuntr (author)andrewc2832017-01-30

I assume you are referring to the step that says "remove any second numbers +/- 2 from third number"

it simply means...

Take your third number. In this case, it is 20.
+/- 2 from 20 is going to be any number from 18 to 22
Remove those from your list of 2nd numbers.
So, in your case, you are only removing 18 and 22 from your list.

andrewc283 (author)2016-08-02

I know that my third # is 20 cuz the last five # were 6, 16, 20, 26, and 36. I got 10 1st #s 0,4,8,12,16,20,24,28,32, and 36. I got 10 2nd #s 2,6,10,14,18,22,26,30,34,and 38.
How do i make twenty combinations left. I dont get the next step.

davidh633 (author)2016-07-16

Does not work in my purple master lock. Middle number are all 1, 4, 7.5, 11, 14... so no number is left after crossing the "repeating ends".

ThomasS261 (author)2016-07-04

While I was doing this I forgot to skip the 2nd numbers that are within +/- 2 of the 3rd. As it turned out, one of those is correct. Since you can get a lock where the 2nd number is within 2 of the 3rd, those shouldn't be taken out.

Twentytwo22 (author)2016-05-20

okay I have a master lock with 19 numbers. Will this still work??

whisper83 (author)2016-05-17

well i bought a new one and it is not getting unlocked no matter what i tried and i know the combination

tdragovich made it! (author)2016-01-07

Thanks, over the years I have had MANY combo locks. gym, lockers at work, storage sheds, oh and don't forget the military... as soon as I wrote down possible for first and second number it came back. Great job.

RSaunders1763 (author)2015-11-18

Wow! Actually worked. Got it in 5 minutes.

ababypenguin (author)2012-09-11

37-11-25 Thanks friend ;)

as long as we're sharing numbers her how about you're social security number, kidding don't share that online bad idea

Thanks for the warning, but this padlock isn't necessarily guarding anything valuable :p Hence why I felt safe enough to share the combo.

molonlabe (author)2015-09-06

Seriously, thank you. I had watched videos and used that guys little formula and for w/e reason my resistant number wasn't that resistant, so it would have taken me forever, but yours worked perfectly.

Ryan Holland (author)2015-01-07

Wow, worked like a charm. Thanks!

eballam (author)2014-09-08


Totally worked!

demogorgon (author)2014-02-05

It works!!! I was about ready to give up, I had already done over 70 combinations and then my lock opened! Great instructable!

wbothun (author)2013-10-02

I was able to do this in 10 minutes - but I knew the first number so it was a matter of trying the middle number. I got it in 2 tries.

Great instructions -thanks!

ide león (author)2012-12-20

Didn't work for me... I've got 32 as the last number 1st number = 0,4,8,12,16,20,24,28,32,36 2nd number = 2,6,10,14,18,22,26,30,34,38 I go CW 3 times, then I stop in 1st number, then I go CCW passing 1 time infront of 1st number before I hit 2nd number, then I go directly to 32 (3rd number) = nothing I did it 3 times already... I'm sure about the numbers, I think is the way I'm spinning the dial. I need some insight???

hulldesign (author)2012-08-30

This worked on a lock I bought in the late 80's. Remembered the correct sequence before I turned the dial on the last combination. Sometimes just setting up the sequences will trigger the memory - if it's a lock you opened a few times. Many years ago. Thanks for the Instructable!

egle14 (author)2012-07-26

what if my third number is a one. what is my remainder?

jrunyan1 (author)2011-11-25

Easier way, just cut an "M" out of a pop can, fold in the two sides so it lookes sorta like a t, wrap it around the Pole , push down, squeeze, and pull

evindrews (author)2011-09-17

So I can't use 12 and 8? Because the last number of my combination IS 12. also, if you get stuck on 3.5, do I move the lock wheel to 4, or 5?
And how Exact DO I need to be doing the numbers?

adavis34 (author)evindrews2011-11-22

no its you need to FIND 12 #'s not 8 #'s

riff raff (author)2011-11-18

Ha! It worked! Had an old Master lock in the junk drawer; no one could remember the combination. Got it on the 18th try. Thanks!

rshaw94 (author)2011-10-10

i went through all your steps using a lock with the key slot on the back, and did all the combinations but no luck /: thanks though.

noremakk (author)2010-07-19

"Now remove any 2nd numbers +/- 2 from your third." What does this mean? Do I remove the numbers from the second list that are within two numbers of the third?

Yes, I think that you remove any numbers from the list of 2nd numbers that are within 2 of your 3rd number. For example, if your 3rd number is "38", you would remove 36, 37, 38, 39, and 40 from your list of 2nd numbers (if they are on that list). I'm still trying out this technique, but that's what I think Step 5 meant.


Yep! Just worked for me. Doublecheck your numbers, and be patient! Keep track of the numbers you tried. Nice instructable!

platinum15 (author)noremakk2010-10-28

i think if its a negative number, you add -2, and if its a positive number, add +2. see if it works and sorry if im wrong :P

jdollar (author)2010-05-05

I think I found a way to narrow the possible "try" combinations down to only TEN.

I think that I found a way to discover what the FIRST number in the three-number combination is. So if you have the first and the last number you only have to try ten combination AT MOST, to find out what the correct one is. 


bombtech91 (author)2007-11-29

anoher way to narrow combos is to remember... First number is always LARGEST.. se4cond number is usually smallest.. and you have she last... don't feel like doin the math, but that removes quite a few possibilites

jdollar (author)bombtech912010-05-05

The first number is NOT always the largest.
I have one that is 18-24-34  master lock is purple in color.


chaosrob (author)bombtech912008-09-11

Maybe for all the locks that you've seen. I have one that is 0-20-26. Hmmm, unless you think the "0" is considered the highest number (on combo locks)

MoeMonkey (author)chaosrob2009-06-23

my lock goes up to 39 like I think most Master Locks so I guess 0 is like the Ace in Cards, it has too numbers, 0 can be 40

DaPaulness332 (author)bombtech912008-11-11

yea, mine's 9-12-19 for school

Sypran (author)bombtech912008-04-29

not true my old locker combo before i switched lockers was 17 47 43...

bowmaster (author)bombtech912008-01-25

My school lock combo is 1-27-1 I just broke your theory and last year my combo was 13-19-13

howboutitbru (author)bombtech912007-12-08

no always man my pe one starts with like something aroudn 9 nad my third number is 35... 35>1st number

howdoesthiswork (author)2010-03-24

 There's an app for that! Crack a combination lock by ear with the iPhone app called "Padlock!" Pretty fun!

left4dead4432 (author)2010-03-20

i have done that before i just opened the backside of it and opened all the way through and it just fell apart.

Peekadosies (author)2010-01-14

You put Step 5 in step 4

pete54321 (author)2009-12-28

 with step three, you chose 19 out of 12 possible numbers, how do we know which number to choose?
also i read on another site that you should cross out all the numbers which arent whole numbers, should we do the same?

RobotWoods (author)2009-10-24

 There's also the new iPhone App 'LockGenie' which helps crack the combinations and does all of the combination prep for you.

tomtortoise (author)2009-10-12

sorry switch 1st and 3rd

tomtortoise (author)2009-10-12

i got to this step and my numbers are 1st 21
                                                                     2nd 3,7,11,15,19,23,27,31,35,39
                                                                     3rd 1,5,9,13,17,21,25,29,33,37
and if i remove any numbers +/- 2 from the third i lose all of the numbers

r3nrut (author)2009-09-28

can zero be a number?

wiilikepi (author)r3nrut2009-10-04

yes =D

memyselfand1 (author)2009-09-12

We have these on almost every one of our school lockers. Some things we do are: 1. kick them. They won't open if you do it enough 2. watch people entering their codes, then put their lock on backwards 3. switch peoples locks around so there is a whole myriad of possibilities with these locks.

aj301292 (author)2009-08-12

this could work. i just tryed it on my locker code for school, which is one of the ones with a key lock in the back, for teacher inspections. this theory workes because with these locks close enough is good enough

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