Gun safe steel gauge explained: what 10, 12 and 14 gauge mean in inches

Steel gauge is the most quoted number on a gun safe's spec sheet, and one of the easiest to misread. It runs backward, so a smaller number means thicker steel. The steps between common gauges are measured in hundredths of an inch. And the number on the box usually describes the body, not the door.

None of that makes gauge useless. It is one of the few construction facts a maker publishes in a form you can convert and compare. This guide gives you the conversion, shows where each gauge turns up in real safes, and explains why we still rank a listed safe above a thicker unlisted one. We haven't measured any safe's steel ourselves: gauge figures come from each maker's published specs, and the inch values come from standard gauge charts published by steel and fastener suppliers.

Gauge to inches: the chart

These are standard (mild) sheet-steel values from Metal Supermarkets' gauge chart, with 3, 19 and 21 gauge from All Points Fasteners' chart, which runs from 3 to 36 gauge and matches on every shared row. Metal Supermarkets notes that actual thickness will vary due to tolerances, and that gauge systems differ by metal: 18-gauge steel is 0.0478 in, but 18-gauge aluminum is 0.0403 in.

Some makers publish millimeters instead of gauge. Barska lists a 3 mm steel body on its AX13106 jewelry safe, which works out to about 0.118 in, between 12 and 11 gauge. A plate door is usually given as a fraction of an inch: 1/4 in is 0.25 in, more than three times the thickness of 14-gauge sheet.

10 vs 12 vs 14 gauge: how big are the steps?

Each step from 14 to 12 to 10 gauge adds the same 0.0299 in, about three hundredths of an inch. In relative terms that is a real difference: 12 gauge is about 40 percent thicker than 14 gauge, and 10 gauge is about 29 percent thicker than 12. Put another way, 10 gauge is just over 1/8 in, and 7 gauge is just under 3/16 in.

Thicker steel also means a heavier safe. Stealth sells two gun safes in the same 55 x 20 x 17 in footprint: the 14-gauge EGS14 at 230 lb and the 12-gauge UL14 at 365 lb. Steel isn't the only difference (the UL14 also has more and larger bolts, working in four directions instead of two), but the pair shows what heavier construction does to delivery and floor load. Weight is part of the protection, too: a heavier safe is harder to carry off, though anchoring does that job better.

Is 14 gauge steel good for a gun safe?

It is fine for keeping children and casual hands out, which is the job of our access-box tier. It is thinner than California's 12-gauge single-wall minimum for gun safes. And in our registry, no 14-gauge gun safe carries a UL RSC burglary listing. If burglary is on your list, treat 14 gauge as a first safe, not a final one.

Is 12 gauge steel good for a gun safe?

It is the most common gauge among the UL RSC-listed gun safes we track, and every RSC-listed gun safe in our registry uses 12 gauge or thicker for its body. Twelve gauge is also California's single-wall benchmark. For a home gun safe it is a reasonable baseline, provided the rest of the evidence is there.

Doors vs bodies: the number on the box is usually the body

Most gun-safe specs lead with body gauge. Doors are built differently and often described differently, so read the door line on its own:

• Composite doors. Steelwater describes the Heavy Duty 20 door as a 4 7/8 in composite with two layers of fireboard. That thickness includes insulation, so it tells you nothing about the steel. Liberty's Presidential door is a composite with a 1/4 in inner steel plate.
• Plate doors. AMSEC gives its door steel as plate: 1/4 in on the NF6036, 3/16 in on the SF6030 and 1/2 in on the BFX6030. Hollon pairs a 3-gauge door (0.2391 in) with a 1/4 in hard plate on the RG-22.
• Same gauge throughout. Stealth publishes matching door and body gauges: 12 on the UL series, 14 on the EGS14.
• Door not published. Kodiak and Winchester publish body gauge for the KGX5933W and Ranger 26 but no door steel figure. When the door isn't published, ask the maker for it in writing.

Two practical rules. First, overall door thickness is not steel thickness. Second, an unpublished door spec is a question to ask, not a reason to assume the best. Our list of gun safe red flags covers other spec-sheet gaps, such as "heavy duty steel" with no gauge at all, which is how Cannon describes its American Eagle series.

Gauge on pistol boxes and gun cabinets

Smaller containers use a much wider range of steel, and the gauge says a lot about the job each one is built for:

• Heavy pistol boxes. Fort Knox publishes a 10-gauge body and a 3/16 in plate door for its Original Pistol Box, the heaviest published steel among the handgun boxes in our registry.
• Mid-weight quick-access safes. Vaultek's MX Series pairs a 14-gauge body with a 12-gauge door; Hornady's RAPiD Safe 4800KP uses 14-gauge steel.
• Light boxes. V-Line's Top Draw XD and Desk Mate and Hornady's Lock Box XL use 16-gauge steel (0.0598 in); Vaultek's DS2i uses 18 gauge (0.0478 in).
• Gun cabinets. Surelock's Combat 10 cabinet publishes a 21-gauge body and a 19-gauge door. At 0.0329 in, 21 gauge is less than a third the thickness of 12-gauge sheet. Cabinets like this are for keeping children and casual hands away from long guns, and our gun safe vs gun cabinet comparison explains where that stops.
• No steel at all. Some cases are polymer. Vaultek's LifePod 10, for example, is a non-metal case, so gauge doesn't apply.

For a small box, gauge matters mostly alongside mounting: a light box that is bolted down or cabled in place is a different proposition from the same box sitting loose on a shelf.

California's steel benchmarks (11 CCR §4100)

The clearest published steel minimums for gun safes in the US come from California's gun-safe standard, 11 CCR §4100. Converted with the chart above, they read like this:

Two details stand out. The door minimum is well above the body minimum: one layer of 7-gauge plate is about 70 percent thicker than 12-gauge sheet. And the whole list is optional: §4100(b) accepts, instead, a safe listed as meeting UL's Residential Security Container standard by a Nationally Recognized Testing Laboratory. Our California DOJ gun-safe guide covers the rest of the standard and how to check a maker's claim.

Why gauge is one input, and a listing tells you more

A gauge figure describes one sheet of the safe. A UL RSC listing describes the finished safe under attack. UL's notice on the RSC standard describes Level 1 as a five-minute attack by one technician using "common hand tools such as drills, screwdrivers and hammers." The test is run on the finished safe, so the result reflects the steel, bolts, hinges, door fit and lock protection working together, not one sheet in isolation.

That is why we rank a listed 12-gauge safe above an unlisted safe with heavier published steel. Hollon's Republic RG-22 publishes a 10-gauge body and a 3-gauge door, far more steel on paper than Stealth's 12-gauge UL14. But Hollon names no UL burglary listing, so nobody outside the company has measured how that steel performs as a safe. Stealth's UL14 carries a maker-stated UL RSC listing. In our rubric the independent listing is worth 30 percent of a gun safe's score and construction 20 percent, as set out on how we rate.

How to read a gauge claim

1. Find the body and the door separately. If only one is published, you know half the story.
2. Make sure it's steel. Gauge numbers mean different thicknesses in different metals, so a gauge with no material named isn't comparable.
3. Convert millimeters. Divide by 25.4 to get inches, then compare with the chart.
4. Add up double walls. AMSEC's BFX6030 has an 11-gauge outer wall and a 12-gauge inner liner, per a retailer spec sheet: 0.1196 plus 0.1046, or about 0.224 in of steel in total. California's standard counts the sum for two-walled safes.
5. Separate door thickness from door steel. A thick composite door is mostly insulation.
6. Treat words as missing numbers. "Heavy duty," "thick" or "solid" steel with no gauge is an unpublished spec.
7. Allow for tolerance. Chart values are nominal; the supplier notes that actual thickness varies.

Six products compared on published steel

From a thin-steel gun cabinet to Liberty's heaviest series. Notice that the burglary rating doesn't simply follow the gauge: the thickest unlisted safe here has no rating, and the listed safes run from 12 gauge to 7.

Listed safes at three steel weights

Pick the listing first, then the steel. These three all carry UL RSC listings and publish their steel, from a 12-gauge closet-sized safe to Liberty's 7-gauge Presidential. If budget decides it, our best-value gun safes show where extra steel is and isn't worth paying for.