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Body Armor Levels | Ratings Compared - Atomic Defense

Body Armor Levels | Ratings Compared

NIJ Level Comparison of Body Armor

NIJ Level Comparison of Body Armor

Different weapons pose different levels of threat. As such, different body armor products offer different levels of ballistic or knife stab protection.


The U.S. National Institute of Justice (NIJ) created the standards to measure protection levels. NIJ also works very closely with the UK Centre for Applied Science and Technology (CAST) to develop globally accepted body armor standards.

As such, body armor that has satisfied a certain NIJ standards level will have satisfied CAST standards for that level, as well. The NIJ also works closely with the Federal Bureau of Investigation (FBI) and the National Institute of Standards and Technology (NIST) to develop their standards. 

Ballistic threat levels are explained in terms of the size and speed of bullets that the body armor at that level can stop. Before you purchase body armor, you need to fully understand the level of threat you are facing based on NIJ standards. The same standards are used to ensure military personnel and law enforcement officers are wearing body armor that offers optimal protection while in an operation.

Below, we explore the various body armor protection levels as per these threat categories.

NIJ Body Armor Levels

Ballistic threats are arguably the most faced threat by people in the modern world, so many people seek to protect themselves against them. NIJ has a very comprehensive body armor ballistic protection level rating system ranging from level IIA to level IV. As you can likely guess, higher levels mean more body armor thickness, weight and protection.

Basically, more layers of ballistic fiber are added to the body armor to make it more protective with each rise in level. This addition is a delicate process, though, as body armor weight is a very crucial factor. Nobody wants to be wearing ridiculously heavy body armor, especially military personnel. It would hinder maneuverability and speed. For them, one kilogram could be the difference between life and death.

NIJ then tests these armor levels in conditioned and new states. Conditioned armor is tested to different environments, like high heat or humidity. With that, NIJ gets conditioned and new armor test numbers, and you get armor that's been tested to an environment you may find yourself in.

Here is a summary table of the latest NIJ Ballistic Protection Standards.

Bullet Features

Level IIA

Level II

Level IIIA

Level III

Level IV

Bullet Caliber

9 mm Luger

.40 S&W

9 mm Luger

.357 Mag

.357 SIG

.44 Mag

7.62 mm NATO

30.06 M2 AP

Bullet Weight

8.0 g (124 gr)

11.7 g (180 gr)

8.0 g (124 gr)

10.2 g (158 gr)

8.1 g (125 gr)

15.6 g (240 gr)

9.6 g (147 gr)

10.8 g (166 gr)

Bullet Diameter

9 mm (.355 in)

10 mm (.400 in)

9 mm (.355 in)

9.1 mm (.357 in)

9.0 mm (.355 in)

10.9 mm (.429 in)

7.62 mm (.308 in)

7.62 mm (.308 in)

Muzzle Velocity in fps (feet per second)









Armor Thickness







NIJ Level IIA Body Armor

NIJ level IIA is the most basic body armor protection leveltested using a 9mm Full Metal Jacket (FMJ) bullet traveling at a speed of 1,225 feet per second (ft/s) new, 1,165 ft/s conditioned. It's further tested by firing a .40 Smith & Wesson (S&W) FMJ bullet traveling at 1,155 ft/s at new armor, 1,065 ft/s for conditioned armor. Body armor is certified as level IIA compliant if it can stop these bullets, which, going by the speed, are obviously fired from small and lightweight handguns.

As expected, the NIJ has very careful and specific guidelines that must be followed when testing out the body armor in the lab. A lot goes into this testing — it's a pretty important process, after all. 

When testing armor levels IIA through IIIA, for instance, the compliance test group consists of 28 complete armors, each one being tested with two threats. With flexible armor in the form of tactical or concealable jackets or vests, 14 complete armors per test threat make up the compliance test group. If special testing needs to be performed with additional threats, the compliance test group will need another 14 complete armors for each additional threat. 

Keep in mind that body armor standardization is not just about preventing penetration. A bulletproof vest could stop the bullets mentioned above but still fail level IIA certification if it cannot reduce the blunt trauma caused by the bullets. In fact, level IIA could stop the bullets used in testing level II body armor from penetrating, but the blunt trauma would still be dangerously high.

Level IIA body armor is very lightweight and usually under 10 pounds, making it easy to conceal and comfortable to wear. It consists of a few thin layers of aramid fibers or any other ballistic fibers. Level IIA body armor is commonly used by civilians and law enforcement officers who are seeking protection against low-impact bullet fire. 

Bulletproof vests in level IIA have a maximum thickness of 4mm. If any of the bullet fire mentioned above hits you while wearing effective level IIA body armor, the worst you could suffer is a bit of blunt trauma, which is unlikely to cause an injury.

With uncertainties regarding the types of weapons people are using on the streets or anywhere else, level IIA body armor is slowly falling out of favor. Many people are skeptical about it and would not want to take chances. That's why level IIA body armor products are mainly special order items nowadays

To recap, here's a quick rundown of level IIA body armor: 

  • Stops 9 mm FMJ and .40 S&W FMJ traveling from small handguns. 
  • Cannot protect against rifle fire or reduce blunt force trauma. 
  • Is easily concealable and best used for officers and civilians facing low-impact bullet fire. 

NIJ Level II Body Armor

Level II body armor is slightly thicker and heavier than level IIA body armor. It can stop and absorb trauma from bullets with higher impact. New level II body armor is tested using a 9mm FML RN bullet moving at a speed of 1,305 ft/s. Conditioned armor is tested at 1,245 ft/s. This is the same bullet used for level IIA, but in this case, it is moving faster hence higher impact. 

The body armor is also tested using a .357 Magnum Jacketed Soft Point (JSP) moving at a speed of 1,430 ft/s new and 1,340 ft/s conditioned. This kind of firepower is still from a handgun, but the handguns used in this case are stronger than those used in level IIA tests.

NIJ level II body armor will stop all of the bullets mentioned above, and those mentioned in level IIA. The extra thickness is to ensure the armor can provide ample protection against the trauma from the higher impact bullets. Although level II body armor is heavier than level IIA body armor, it's still incredibly lightweight, comfortable to wear and easy to conceal.

Level II body armor has a maximum thickness of 5mm. Bulletproof vests in this category feature several layers of Kevlar or other aramids. However, a drawback to this level is that it can't protect against rifle bullet fire. While it can stop some of the bullets used to test level IIIA body armor, the blunt trauma would be too much and could possibly cause an injury. 

Level II body armor is commonly used by council workforce officers. The armor provides them with protection against handgun fire, as well as physical assault. It also ensures it does not weigh them down too much — they can maneuver and move around without fatigue. It is a favorite of many civilians as well.

So, here are the basics regarding level II body armor: 

  • Stops 9mm FML RN and .357 Magnum JSP. 
  • Cannot withstand rifle fire. 
  • Is comfortable, lightweight and easy to conceal. 
  • Is best for council workforce officers and civilians seeking protection from handgun fire and physical assault. 

NIJ Level IIIA Body Armor

Level IIA body armor still provides protection against handgun fire, but it's sturdier than level II body armor. Level IIIA body armor is tested using a Flat Nose (FN) .357 SIG FMJ bullet moving at a speed of 1,470 ft/s for new and 1,410 ft/s for conditioned armor. It's then further tested using a .44 Mag Semi-Jacketed Hollow Point (SJHP) bullet, moving at a velocity of 1,430 ft/s for new armor, 1,340 ft/s for conditioned

Note that these bullets are heavier and travel faster than those used in testing level II body armor. Level IIA body armor can also protect against 9mm and .44 Mag. bullets shot by a submachine gun. 

Level IIIA body armor delivers the perfect balance between protection level and comfort. It's quite protective against most handgun-shot bullets and still has a decent level of comfort for the wearer. Although not as light as level II body armor, it's not considered heavy. It is still quite easy to disguise as well. Level II body armor delivers more comfort than level IIA body armor, but at the expense of losing some level of protection.


Getting hit by a 9mm FMJ bullet traveling at a speed of 1,225 ft/s, similar to the one used to test level IIA body armor, while wearing level IIA bulletproof vest is like getting hit by a small rock. It cannot penetrate, and the trauma is completely subdued. The most you’d suffer is a slight sting. 

The .357 SIG FMJ FN and .44 Mag SJHP used in the tests would cause more impact and possibly sting more, but they would still be subdued. They are highly unlikely to cause injury. Level IIIA body armor is quite effective in subduing blunt trauma and will allow the user to return fire even after getting hit.

Level IIIA is the highest level of soft body armor. Soft and hard body armor are distinguished by the materials used in their manufacture. Soft body armor is made with soft ballistic materials, and it is lightweight and flexible. On the other hand, hard body armor is made of toughrigid materials and it is bulky. The next levelslevel III and IV, consist of hard body armor.

Keep in mind that bulletproof vests, which are the most common body armor products, are a combination of ballistic plates and plate carriers. The vest itself is just a carrier, and it only becomes bulletproof when the ballistic plates are inserted.

A good thing is that you can use one plate carrier with ballistic plates of different levels. That allows you to raise your body armor’s level of protection without necessarily having to purchase another complete bulletproof vest.

You also need to ensure the armor fits properly and that the ballistic plates fit in the carrier, as armor plates and panels come in different sizes. 11x14 inches and 10x12 inches are most commonly offered on the commercial market, so nearly any vest will accommodate one of these plate sizes. 

For instance, if you were to get hit with the caliber used to test level IV armor while you're wearing level III, it would likely shatter the bullet into pieces then continue into your body — not a fun situation to be in, if you ask us. That's why it's essential to have armor that will stop the highest threat you'll potentially be facing. 

A “soft” IIIA can easily stop smaller rounds such as 9mm and .22. However, if you want to stop rounds like 7.62 or 5.56 from an AK-47 or AR-15, you'll need a level III instead. Most manufacturers' level III armor will only stop 7.62 fired from AK-47s — however, all of our level III armor at Atomic Defense can stop the most commonly used 5.56 bullets from AR-15s, too. Typically, IIIA can only stop these larger rounds if the bullet hits you at an extreme angle. Even then, it's highly unlikely. 

Atomic Defense's level IIIA armor can also stop 12 gauge slugs and buckshot. What can we say? We go above and beyond the industry standard to give you the best armor. 

To recap, here's everything you need to know about level IIIA body armor: 

  • Stops .357 SIG FMJ FN, .44 magnum rounds and 9mm FMJ. 
  • Subdues blunt force trauma. 
  • Is sufficient for civilians, federal government forces or law enforcement facing heavy gunfire threats. 

NIJ Level III Body Armor

Level III takes everything to a whole new level that involves serious gunfire and threats. Designed to protect against rifle gunfire, level III body armor is tested using a 7.62 mm FMJ steel jacketed bullet traveling at a speed of 2,780 ft/s — in this level and the next, NIJ only tests conditioned armor. Such speed is provided to the bullet by NATO classified rifles. This is some serious gunfire that can drop someone dead in an instant at longer ranges.

Regarding NIJ testing standards, the required number of armor samples depends on the armor type. When testing level III hard armors and plate inserts, the compliance test group consists of nine armor panels. These types of armor are subjected to a 24-shot Perforation-Backface Signature (P-BFS) test, as well as a 24-shot Baseline Ballistic Limit (BL) test. 

      Additionally, the panels need to be large enough to allow for a minimum of six shots per panel, but they also can't exceed a size of 10x12 inches for testing. As you can see, the NIJ is pretty nitpicky when it comes to testing body armor — but they kind of have to be, right? 

      Remember that most manufacturers' level III body armor will only stop 7.62 from AK-47s. Not to toot our own horn, but all of our level III armor made by Atomic Defense can stop the most commonly used 5.56 bullets from AR-15s as well. 

      Level III body armor must have solid ballistic plates. In some instances, the carrier vest is soft body armor in itself and could rank as level IIA or IIIA. When the appropriate hard armor plates are inserted in the carriers, they are retested to ensure they are up to the level III standard. Such carrier vests are clearly labeled to indicate they only provide level III protection when they have the appropriate ballistic plates on.  

      The most common armor plates are:

      • 6mm/¼’’ ballistic steel plates
      • 13mm/½’’ ceramic plates
      • 25mm/1’’ Polyethylene plates

      The hard ballistic plates significantly increase the weight of Level III body armor as compared to the lower levels. This kind of body armor is also quite difficult to disguise, so it's more common with trained officers in tactical forces. They use it when they are facing confrontations that involve serious gunfire. 

      While civilians are free to purchase and use such body armor, it would be too heavy for them. They would find it hard to maneuver around while carrying out ordinary day-to-day activities. It is, therefore, not very popular among civilians.

      The level III armor plates are metal-like. The carrier vests are also quite thick. The bullets and rifles mentioned above are very powerful. In most instances, such gunfire will drop you down when you get hit, even when you have level III body armor on, but it will not penetrate. If you were to get hit with the kind of gunfire used to test level IV body armor while wearing level III body armor, it would still not penetrate but the trauma would be too much and dangerous.

      Another important consideration of body armor is how SAPI and ESAPI plates (what the heck are those?) relate to these NIJ levels. SAPI body armor, which stands for small arms protective inserts, is typically used by the U.S. military. It's usually made from ceramic with an external composite coating. It comes in several sizes and ranges in weight from 3 pounds to 5.5 pounds, meaning it's a lightweight option allowing for sufficient mobility. Most SAPI body armor has a level III NIJ rating. 

      ESAPI, which stands for enhanced small arms protective inserts, are essentially upgraded versions of SAPI plates — the name makes it pretty obvious. These options are designed to meet NIJ level IV protection, so you can likely imagine they're a little heavier and denser, though they're almost identical in size and shape to SAPI plates. 

      Most ESAPI plates are created from high-quality boron carbide ceramic, a material commonly used for armored vehicles like tanks. They're usually unavailable to the average civilian, as they've become a new standard for the military. 

      Before we move on to the final level, here's a quick recap of level III armor: 

      • Stops 7.62 mm FMJ steel jacketed bullet rounds — Atomic Defense stops 5.56 bullets from AR-15s, as well. 
      • Protects against rifle gunfire but is difficult to disguise. 
      • Is most common with trained officers in tactical forces. 

      NIJ Level IV Body Armor

      Level IV is the highest NIJ standard of protection that body armor can provide. Bulletproof vests in this category also consist of carrier vests and hard ballistic plates, which are tested together as a unit in order to certify them as level IV

      Level IV body armor is tested using a 30.06 M2 AP (Armor Piercing) bullet moving at a speed of 2,880 ft/s — remember that this speed is for conditioned armor, not new. 30.06 was considered a favorite caliber among GIs back in WWII due to its advanced terminal performance. When loaded with AP M2 ammunition, the M1 rifle could penetrate protective barriers more effectively to reach the enemy, as well as lightly armored vehicles. 

      For body armor intended to provide level IV protection, the compliance test group needs a sufficient number of armor panels allowing a 24-shot P-BFS test and a 12-shot BL test with at least one spare armor panel. 

      This kind of gunfire is shot from an assault rifleLevel IV body armor can stop the bullet and absorb some of the trauma, although the impact will still be a bit high and might throw you backward

      The carrier vest of soft armor on its own must satisfy certain NIJ conditions to be considered level IV armor. It can't offer level IV protection on its own — the inserts have to be on for optimum protection. The carrier vests are clearly labeled to indicate what level of protection they offer and which inserts are needed for them to be level IV bulletproof vests. 

      A commonly used level IV insert is the 18mm/¾ ‘’ ceramic plate. Another popular level IV plate is the 12mm/½’’ ballistic steel plate, although it is too heavy to be used as body armor. It is mainly used as vehicle armor.

      As expected, level IV armor is bulky and basically impossible to disguise. It'd be difficult for any untrained person to use this body armor — heck, putting it on is a challenge in itself. Level IV body armor is mainly issued to military officers and other security forces who might go to combat or find themselves in highly confrontational environments. 

      While there's a lot of uncertainty on the streets today, it's highly unlikely there are civilians facing ballistic threats that would necessitate them to wear level IV body armor. However, people like journalists who film in conflict-laden areas might need to use level IV body armor.

      As mentioned earlier, all the body armor in level III and level IV is classified as hard body armor. We’ve already seen that it is heavy and rigid. It is important to mention that, even with all this toughness, no single body armor can be said to be 100% protective. You cannot have body armor covering every single inch of your body. As such, even while you have body armor on, you are still exposed to risks. You should remain cautious if you are facing any ballistic threats.

      Here's a brief rundown of IV body armor to wrap up the NIJ ballistic threat levels: 

      • Stops 30.06 M2 AP rounds. 
      • Require inserts for carrier vests to reach level IV protection. 
      • Is bulky and difficult to disguise. 
      • Is most common for military and security forces in combat or highly confrontational situations. 

      ICW vs. Stand-Alone (STA) Plates

      When comparing the different NIJ threat levels, IIIA is typically viewed as a middle ground between lightness and stopping ability. That's why military and police forces commonly pair a level IIIA vest with a level III or IV insert plate as needed. This versatility is a major benefit to level IIIA body armor — you can use In Conjunction With (ICW) armor plates. 

      For instance, a level III ICW plate may not stop an AK-47 on its own, but a Stand-Alone (STA) level III will likely have no problem doing so. STA means it can achieve the desired NIJ rating on its own. We don't mean to brag, but at Atomic Defense, we sell STA plates exclusively. This means our armor doesn't require additional armor behind it to complete the important task of stopping high-level calibers. 

      NIJ Levels for Stab Resistance

      Contrary to popular belief, body armor isn't just designed to protect against ballistic threats. Body armor can be used while facing other threats such as knife stabs and fire. In that regard, NIJ works with CAST to develop standards for body armor protection against knives and edged blades. The three stab resistance levels described under NIJ Standard 0115.00 are:

      • Level I: As you can probably guess, level I offers the least amount of stab resistance. This level protects against low-energy threats with a strike energy of 24 joules (J). 36 J is the overtest condition here. Armor in this level is made to be concealable, and you can even wear it for an extended time.
      • Level II: Level II protects against medium-energy threats — a strike energy of 33 J, and 50 J is this level's overtest condition. You'll find concealable and unconcealable options.
      • Level III: Level III protects against high-energy threats with a 43 J strike energy, and 65 J is the overtest condition. You'd typically wear this level in high-risk situations, especially because it's unconcealable.

      The table below shows the various body armor edged blade protection levels.


      Knife Resistant Level 1 (KR1)

      Knife Resistant Level 2 (KR2)

      Energy Level






      5 m/sec

      6.2 m/sec

      5.9 m/sec

      7.3 m/sec

      Energy (Joules)





      Weapon Mass

      1.9 kg




      Maximum Penetration






      Because knife crime has increased in large European and British cities — especially London — civilians in these areas often find it necessary to wear body armor that protects more against knives than it does guns. Soft body armor for protection against spiked weapons and edged blades tend to be rigid, thick or a combination of the two. Of course, this is pretty important when there's a knife coming at you. 

      Remember that 20mm of penetration will let the knife tap pass through the armor since most armor that stab resistance rating is used on is thin, soft IIIA or lower rated armor — usually less than a centimeter thick. This may be considered the acceptable standard, but once again, we go above and beyond at Atomic Defense. We ensure our armor stops the blade from passing through. 


      Find the Right Protection for the Job at Atomic Defense 

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      After learning about the NIJ's bulletproof vest levels and bulletproof plate levels, you may find it easier to determine the type of armor needed for your job. Whether you're a civilian or law enforcement officer seeking protection or you're in the military, we have high-quality armor platescarriers and vests for you to choose from. 

      When you spend $200 or more, you can use our promo code AD1010 for $10 off your purchase. Use this link to auto-apply the code at checkout. 

      Need help finding the right body armor? Contact Atomic Defense with questions at any time. 

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