How to Pick a Combination Padlock (and What It Says About Security)? | Grades Beat Digit Count

Thicker shackles and tighter tolerances cost more, and the numbers that predict how a lock holds up usually sit on the package in small print. Most buyers never look at them, then wonder why a cheap four-dial lock pops open while a certified one shrugs off the same abuse. The grade code is the whole story.

Picking a combination padlock for a gate, shed, or toolbox means matching a tested security level to what you’re actually protecting, and understanding that combination locks are built to stop casual access, not a determined attacker with tools and time. The two questions below decide almost everything.

How Secure Is A Combination Padlock, Really?

Not very, against a serious attack — combination padlocks are designed to deter casual access, and their security is measured by standardized attack-resistance tests, not by whether one picking trick works. That’s a useful reframe, because it means you’re shopping for a certified performance level rather than a clever mechanism.

Public padlock standards focus on environmental, functional, and security requirements, plus durability, corrosion resistance, and simulated attacks. They don’t promise a combination padlock can’t be opened by manipulation. One summary of the European standard BS EN 12320 states plainly that “human intervention, durability, manipulation and picking tests are not included in this standard” — so a certification mark tells you how a lock survives attack testing, not that it’s unpickable.

What actually moves the needle in the real world:

• Build quality and tolerances. A lock with sloppy internal clearances gives an attacker more feedback to work with.
• Shackle and body design. Hardened shackles and a shielded body resist cutting and prying far longer.
• Certification grade. An independent test result beats any marketing claim about dials or digits.

Digit count is the weakest signal in that list. A ten-digit dial doesn’t guarantee a hardened shackle, and a well-built three-dial lock from a certified line can outperform it on every attack test that matters.

Combination Padlock Security Grades: What The Standards Measure

The world’s padlock standards use numbered security grades to rank attack resistance, and each region runs its own system — they are not interchangeable. Matching the grade to the job is the standards-based way to “pick” a padlock for security, rather than choosing purely on price or convenience.

Two traps live in that table. First, mechanical padlocks and mechatronic padlocks follow different standards, so a grade from the electronic world tells you nothing about a dial lock. Second, a U.S. ASTM rating, a European EN grade, and an Australian AS grade come from different test regimes, so a “Grade 6” on one label isn’t automatically equal to a “Grade 6” on another.

For building applications, BS EN 12320-style classifications are described as being based on performance tests that simulate attack, which is exactly the number worth comparing when two locks sit side by side on a shelf.

Matching A Grade To The Job

Buy the lowest grade that genuinely fits the value of what you’re locking and the time an attacker could work undisturbed. A garden gate latch facing a public sidewalk and a storage unit behind two locked doors should not get the same lock — and the standard frameworks exist so you can make that call with test data instead of guesswork.

Practical rules that hold up:

1. Check the label for a standard reference — ASTM F883, EN 12320, or AS 4145.4 — before you check the dial count.
2. Buy above the minimum when the item is expensive or the location is quiet. An attacker with privacy gets more attempts.
3. Match the finish to the weather. Corrosion resistance is part of what these standards test, and a seized lock is a failed lock.
4. Skip the electronic blur. If a lock uses electronic keys, EN 16864:2017 is the relevant framework, not the mechanical grade you were comparing.

One caution that applies across the board: these are product-performance standards, not end-user compatibility guides. They tell you how a lock resists attack, not whether it fits your hasp or survives your particular climate. If you want tested options already narrowed down, our roundup of the best combination padlocks for garden use compares models on exactly these build and grade factors.

The Short Version

Security for a combination padlock is a certification question, not a dial-count question. Match the grade to the application, verify the lock carries a recognized standard reference, and accept what these locks honestly are: a barrier against casual access, backed by a tested resistance level.

The current ASTM padlock specification is ASTM F883-13(2022), the European padlock standard EN 12320 carries six grades with Grade 6 at the top, and the Australian framework AS 4145.4-2002 runs ten grades on attack-simulating tests. ASTM F883-13(2022) lays out the padlock performance requirements that U.S. buyers see on compliant products.