RHA Rolled Homogeneous Armor
The uniform hot-rolled steel armor standard used as the common baseline for measuring both armor protection and projectile penetration in millimeters.
RHA is armor plate made from a single steel composition, hot-rolled to a uniform structure throughout its thickness, as opposed to layered, cemented, or composite armor1. It was the standard tank armor material for most of the 20th century, and even though modern vehicles rely on composite, ceramic, and reactive armor packages instead of plain rolled steel, RHA never stopped being the reference unit the industry measures against. A protection figure or a penetration figure quoted “in RHA” or “RHA equivalent” (RHAe) means the actual armor, or the actual penetrator, performs as well as a given thickness of plain rolled steel would, even when neither one contains any steel at all2. It is a common yardstick, not a literal material description, and because armor geometry, angle, and quality all affect real-world performance, RHAe comparisons between different systems are only ever approximate.
On WeaponSpecs, this is the same convention behind the munition.penetrationMm field on tank and gun-round entries, penetration figures are RHA-equivalent values at a stated range, not measurements against whatever armor a specific target actually carries. For the full breakdown of how composite armor, reactive armor, and active protection systems stack together against modern threats, see Tank Armor Explained.
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