PROTECTION LEVELS

Body armor is available at different levels of protection, which are standardized by the US National Institute of Justice (NIJ) and the UK Centre for Applied Science and Technology (CAST).

BALLISTIC LEVELS

Ballistic levels of protection outline the exact strength of attack each level of bulletproof body armor can protect against. As the levels go up, you will be protected from a wider range of gun threats. The levels of protection for body armor are: 
NIJ Level IIA NIJ Level II NIJ Level IIIA NIJ Level III NIJ Level IV
Areal Density 3.5 kg/m 42.2 kg/m 5.9 kg/m 25.9 kg/m 32.5 kg/m
Thickness 4mm 5mm 6mm 15mm 20mm
.22mm short X X X X X
.9mm X X X X X
.45mm X X X X X
.380mm X X X X X
.38mm X X X X X
.22mm long X X X X
.44 Magnum X X X
.30 Carbine X X
5.56mm X X
7.62mm NATO X X
.30-06 X X
.30 Armor Piercing (M2 AP) X

EDGED BLADE LEVELS

CAST standardizes stabproof vests and has identified different levels of protection for bulletproof vests. This is because although the materials in bulletproof and stabproof vests are developed in the same way, a stabproof vest requires a much tighter weave and the addition of materials like chain-mail or laminate to be effective. Multi-threat vests that can protect against ballistics and knives will still need to be graded according to the levels outlined above and below:

Knife Resistance Level 1 Knife Resistance Level 2
Energy Level E1 E2 E1 E2
Energy (joules) 24 36 33 50
Velocity 5 m/sec 6.2 m/sec 5.9 m/sec 7.3 m/sec
Total Missile Mass 1.9 kg 1.9 kg 1.9 kg 1.9 kg
Maximum Penetration 7 mm 20 mm 7 mm 20 mm

SPIKED WEAPON LEVELS

Neither bulletproof nor stabproof vests are equipped to protect against spiked weapons, which have standardized levels of protection. Spike protection can be added to stab and bulletproof vests as a laminate coating, but it is important to make sure it adheres to proper testing. The threat levels for spike-proof vests are:

Knife Resistance Level 1 &
Spike Protection Level 1

Knife Resistance Level 2 &
Spike Protection Level 2

Energy Level

E1

E2

E1

E2

Energy (joules)

24

N/A

33

N/A

Velocity

5 m/sec

N/A

5.9 m/sec

N/A

Total Missile Mass

1.9 kg

N/A

1.9 kg

N/A

Maximum Penetration

KR1 = 7 SP1=0

N/A

KR2 = 7 SP2=0

N/A