How to Find Lost Locker Combinations

Many, if not most, lockers require students to supply their own padlocks.

A lost locker combination can mean tardiness or missed assignments, and tardiness and missed assignments can cause a failing grade. If you forget the combination to your lock, you can easily narrow it down to 100 possible combinations using elementary mathematics.

Instructions

1. Turn the lock dial to "0." Pull up on the curved metal locking mechanism and lightly turn the lock dial. At some point within the first seven or eight digits, you will begin to have trouble turning the dial as it starts to stick. Rotate the dial back and forth very gently; the dial will be stuck between two numbers, one digit apart. Write down the average/mean of those two numbers.

   For example, if the dial sticks between the numbers two and three, write down "2.5."

2. Continue moving the lock's dial forward, writing down the average/mean of the two numbers at each sticking point. The dial will stick at 12 points.

3. Cross out all numbers that end with "0.5". Of the five remaining numbers, the one's digit will be the same for four numbers. Cross out those four numbers. The remaining number is the third number in the combination.

   For example, if you see "1, 11, 21, 31 and 36", cross out every number but "36".

4. Divide the third number in the combination by four. Write down the remainder.

   For example, if the third number is 36: 36/4=9, with a remainder of 0. Write "0" on your page.

5. Add four to the remainder. Write that number down next to the remainder. Continue adding four to the last number. Do not pass the number 39, as 39 is the highest number on a Master Lock combination lock. These comprise the possibilities for the first number in the combination.

   For example, if your remainder equals 0, write down "0, 4, 8, 12, 16, 20, 24, 28, 32, and 36."

6. Write "2," if your remainder was 0. For one, write "3." For two, write "0." For three, write "1."

7. Add four to whatever number you got in Step 6. Continue adding four. Do not pass the number 39, as 39 is the highest number on a Master Lock combination lock. These are the possibilities for the second number in the combination.

   For example, if your remainder equals zero, write "2, 6, 10, 14, 18, 22, 26, 30, 34, and 38."

8. Try every possible combination of the numbers you got in steps 3, 5 and 7 on the lock. You may have to try this up to 100 times if your combination is the last set of numbers.

Tips & Warnings

• This method only works for the common MasterLock.

• If your locker contains an inside lock, meaning the lock is attached to the locker, ask your school for the combination to the lock.

• If your lock is an American Lock, you may have to cut the lock. You can access an American Lock through the back of the lock, but many times the back of the lock is inaccessible while locked.

References

• Master Unlocked: Overview of Combination Recovery for Single Dial Padlocks
• Master Unlocked: Finding sticking places and using them to identify the last number in the combination.
• Master Unlocked: Finding Combinations for the Master Locks with Serial Numbers Beginning with 800, and for Locks from Other Manufacturers