The fastest way to open a number lock without the combination

If you've forgotten the combination to a number lock, you have three practical options: try a reset method if the lock has one, use bolt cutters or an angle grinder to cut it off, or call a locksmith. Which one works depends on the lock type and whether you own it or are renting the device it secures.

Most padlocks have no built-in reset, so cutting is usually the quickest solution if you own the lock. If you're renting — say, a locker at a gym or storage unit — contact the facility first, because they may have a master key or their own procedure for locked-out users. A locksmith can open almost any lock without damage, but costs money and takes time to arrive.

The method you choose also depends on what the lock secures. A lock on your own bike or toolbox is yours to cut. A lock on rented equipment or a shared device is not.

Key Takeaways

  • Most number locks have no reset function, so cutting with bolt cutters or an angle grinder is the fastest owner option.
  • If you rent the device the lock secures, contact the facility or landlord first — they may have a master key or replacement lock.
  • A locksmith can open the lock without damage but will charge a service fee and take time to arrive.
  • Bolt cutters work on locks up to about one-quarter inch thick; thicker locks need an angle grinder or professional help.
  • Write down or photograph new combinations when ready after setting them, and store the photo somewhere you can find it later.

Cutting the lock off yourself

If you own the lock and need it open now, bolt cutters are the simplest tool. They cost $15 to $40 new, or you can borrow a pair from a neighbor, tool library, or hardware store rental section. Position the lock's shackle (the U-shaped metal part) between the cutting blades and squeeze the handles together with steady pressure. The shackle should snap in one or two cuts.

Bolt cutters work well on locks with shackles up to about one-quarter inch thick. If your lock is heavier or the shackle is thicker, an angle grinder cuts faster. Angle grinders cost $30 to $100 to buy, or $10 to $20 per day to rent. Wear safety glasses and work gloves — metal shards fly when you cut. Grind across the shackle until it separates from the body, then pry the pieces apart with a flathead screwdriver.

After you cut the lock off, you'll need a replacement. Buy a new number lock at any hardware store or online retailer. Set your new combination to something you can remember, or write it down and store the note somewhere safe — a photo in your phone's notes app works well.

Calling a locksmith to open it without cutting

A locksmith can open most number locks without damage, which matters if the lock belongs to someone else or if you want to keep using it. Call a local locksmith and describe the lock type — they'll give you a price estimate over the phone, usually $50 to $150 depending on lock complexity and your location. Arrival time is typically one to three hours, sometimes longer on weekends.

When the locksmith arrives, they'll use tension and manipulation tools to feel for the lock's internal mechanism and open it. This takes 5 to 15 minutes for a standard padlock. Ask the locksmith to write down the combination for you before they leave, or ask them to reset it to a combination you choose.

A locksmith is your best option if the lock is expensive, if it's attached to something you can't damage, or if you need to preserve it for a rental situation. It costs more than cutting, but you keep the lock and avoid property damage.

What to do if the lock is on rented equipment

If the lock secures a locker, storage unit, bike rack, or other rented item, contact the facility or property manager before you do anything. Many have a master key or a replacement lock on hand. Some will cut it off for you at no charge; others will charge a small fee for a replacement lock.

Explain that you've forgotten the combination and ask what they need from you. Most facilities will ask for your ID and proof that you rent the space. They may also ask you to sign a form acknowledging the lock replacement. This process usually takes 10 to 30 minutes and costs nothing or a small amount.

Never cut a lock off rented equipment yourself — you could be charged for damage or loss of the lock, and the facility may think you're trying to break in. Always ask first.

Resetting a combination lock that has a reset button

Some number locks have a small reset button or lever on the back or bottom. If yours does, you can reset the combination without cutting. Look for a tiny hole or a small lever marked "Reset" on the lock body. Press and hold the button with a paperclip or small pin for 10 to 15 seconds while the lock is in the open position, or follow the instructions printed on the lock itself.

After you reset, the lock will return to its factory default combination — usually 0-0-0 or 0-0-0-0 depending on the number of dials. Open it with the default combination, then set a new one you'll remember. Not all locks have this feature, so check your lock's manual or the manufacturer's website if you're not sure whether yours does.

If your lock has no reset button and you can't find the manual, cutting is usually faster than searching for the manufacturer online.

Preventing this problem with a new lock

Once you have the lock open and a replacement in hand, take steps to avoid forgetting the combination again. Write the combination down in a place you'll remember — a note in your phone, a password manager, or a physical notebook at home. If you use a password manager like Bitwarden or 1Password, you can store the combination there alongside other sensitive information.

Take a photo of the combination written on a piece of paper and store it in a private folder on your phone or cloud storage. This way, if you forget, you can search your photos by date or location to find it. Avoid writing the combination on the lock itself or on a sticky note attached to the lock — that defeats the purpose of having a lock.

If you use the same combination for multiple locks, write that down too. If you change the combination periodically, update your notes each time.

Frequently Asked Questions

Can I open a number lock by guessing the combination?

Theoretically yes, but it's impractical. A three-dial lock has 1,000 possible combinations. A four-dial lock has 10,000. Testing each one takes 5 to 10 seconds per try, so you'd spend 1 to 14 hours guessing. Cutting or calling a locksmith is faster.

Will bolt cutters work on my lock?

Bolt cutters work on most padlocks with shackles up to one-quarter inch thick. If your lock is a heavy-duty model or a chain lock, bolt cutters may not cut through — you'll need an angle grinder or a locksmith instead. Try the bolt cutters first; if they don't cut after 30 seconds of pressure, switch to another method.

What if I cut the lock and damage the thing it was attached to?

If you own both the lock and the object, the damage is yours to repair. If you're renting or the object belongs to someone else, you could be liable for repair costs. This is why contacting the owner or facility first is important — they can tell you whether cutting is safe or if they prefer a locksmith.

How much does a locksmith cost to open a number lock?

Most locksmiths charge $50 to $150 to open a padlock, depending on lock type and your location. Call a few locksmiths in your area for quotes before you decide. Some charge a service call fee on top of the opening fee, so ask about the total cost upfront.

Can I reuse the lock after a locksmith opens it?

Yes. A locksmith opens the lock without damaging it, so you can use it again. Ask the locksmith to reset the combination to something new, or reset it yourself if the lock has a reset button. If the lock is damaged or you don't trust it anymore, buy a replacement.