Armor Damage in GURPS

by Peter V. Dell'Orto

GURPS fans have been blessed by a system that allows you to break shields, shatter weapons, cripple limbs, but even after you reduce your foe's weapons and shield to flinders and his body to -10xHT his armor is still fine.

Until now. The following rules are an extension of the rules for Armor Enchantment in GURPS Magic on p. M46. These rules expand upon those rules, and include further optional rules you can add on to bring this system to the level of grittiness you need for a campaign. This system does require some bookkeeping by GMs and players alike, but not really that much more than the Damage to Shields rules (p. B120) require. These rules add some extra realism to combat as well; armor wears out, requiring repairs and eventual replacement.

Armor Damage

Armor can only withstand a limited amount of destruction -- referred to as Maximum Penetrations -- before it is no longer capable of protection. Armor can take (DR+1)*5 penetrations before becoming useless as protection. For example, Reinforced Heavy Leather (DR 3) can take (3+1)*5=20 penetrations before becoming useless. For armor with split DR, such as chainmail, use the highest DR to calculate the Maximum Penetrations. A penetration is defined as any hit that does damage greater than DR. Blows that do less than or equal to DR do not count as penetrations. Armor divisors do lower the amount of damage needed to cause a penetration, but do not cause additional penetration to the armor. Penetrations are tracked on a per- location basis if using the Hit Location chart; if you use Basic Combat, calculate penetrations based on the torso and count all penetrations as being against the torso armor.

Note that some ultra-tech weapons (Flamers, sonic weapons, etc.) already do armor damage -- the effects should be combined if these rules are used as well. Magic can damage armor as well. As a rule, spells which cause damage reduced normally by armor DR (such as Fireball, Ice Dagger) will inflict penetrations like any other attack, while spells which bypass armor's protection (Dehydrate, Deathtouch) will inflict no penetrations. Some magic can be used to directly attack armor. For example, Shape Metal or Reshape can be used to shape armor completely off a location. Ruin inflicts PD and DR loss per p. M59, which will reduce the Maximum Penetrations by 5 per minute. Shatter and Disintegrate will succeed if the damage inflicted is greater than the Maximum Penetrations of the armor, and destroy that location's armor completely. If they fail, no damage is inflicted. The Weaken spell will inflict 1d6 penetrations per casting. And so on -- a GM's judgment is needed to cover the myriad of magic attacks that can damage armor.

As per GURPS Magic, Fortify and Deflect wear out as well and a little more rapidly. Regardless of any non- magical armor repair, magical armor will become non-magical after 5 times the base DR penetrations (0 base DR would get 5 penetrations). Chainmail would survive 15 penetrations before becoming non-magical, a leather jacket only 5. Both armors would need 5 more penetrations (At base DR, not DR + Fortify, which is gone when the spell is broken) before becoming useless as armor. While base DR is used to calculate the number of penetrations the enchantment can sustain, actual DR (including Fortify) is used to determine if armor has been penetrated. Fortify +5 Heavy Plate (DR 12) may take only 35 penetrations before becoming non- magical, and 40 penetrations before being ruined as armor, but it would take 35 attacks each doing at least 13 damage followed by 5 doing at least 8 each to do this! If the armor is destroyed as armor before an enchantment wears off (say, Light Leather with Deflect +5 cast on it), the enchantment is considered destroyed when the armor is destroyed. Magic such as the Repair spell will repair the enchantments on a damage suit of armor as well as fixing the mundane damages.

When calculating penetrations, only that individual layer of armor counts. If you are wearing a steel breastplate (DR 5) over Fortify +1 light leather (DR 2), you must take 8 points of damage for the light leather to be penetrated, but only 6 damage for the breastplate to be penetrated. Exception: Chainmail and its accompanying Cloth Armor should be treated as one layer for both simplicity and to prevent chainmail from rapidly losing the benefit of its cloth padding.

At no point in this process is PD or DR reduced (but see the various Optional Rules, below). Sealed armor is considered unsealed after it takes 10% of its Maximum Penetrations. Most high- tech sealed armor will have limited self-sealing capabilities; a single penetration is not enough to cause the armor to become unsealed. Note that this is cumulative with the unsealing effects of Flamers.

And yes, if an attack does Blow Through, excess damage is applied to the back of the armor piece. Truly destructive attacks can easily cause double penetrations. This is called an "exit wound."

Armor Repair

Damaged armor can be repaired. This requires appropriate skill (12+ in Armoury, or Leatherworking for leather armor) and materials (ranging from a needle, thread, and cloth patches to a full forge or machine shop). The cost to repair is 5% of the original cost plus the penetrations suffered vs. Maximum Penetrations, expressed as a percentage. After taking more than half of its possible penetrations, the cost is 20% of the original cost plus the percentage taken -- the armor is very badly damaged and needs a full rebuild. Cost assumes you are paying a professional to do the work -- if you do it yourself, cost of repair is halved (the cost is for materials expended). Note that after a certain point, armor can become so damage replacement is cheaper than repair. A Repair spell (p. M60) can be cast as well -- any armor having taken more than half of its Maximum Penetrations should be considered to have missing parts and give a penalty to skill. A penalty to cast the spell is a good justification for a hireling wizard to charge extra, if a GM so chooses. After all, the caster is taking an extra risk of failure or critical failure because of the damage taken.

Ultra Tech repair methods can also affect the cost of armor repair, at the GMs option. If armor is made from Living Metal (p. UT18) or Bioplas (p. UT17) it will slowly repair itself -- Living Metal at 1 penetration/hour and Bioplas at 1 penetration/6 hours. If the materials used in the armor are rare or the technology to repair it is expensive, the cost may increase. This applies to low tech and fantasy armor as well -- perhaps even higher skills (15+ or even 20+) are need to repair armors made from rare or magical materials. Cost will escalate as well -- but note that the base system already scales to make more expensive armor more expensive to fix. Armor that has been decorated (see optional rules, below), or armor of higher or lower quality, uses its increased (or for Cheap, reduced) cost to determine cost of repairs.

Example of armor repair: A heavy plate corselet costs $2300. It can suffer 40 penetrations and has taken 13. 13 is 32.5% of 40. The cost to repair the armor is $115 + $747.50 = $862.50. Plate is durable, but expensive! Had that same suit taken 21 penetrations, the cost would have been $460+$1207.50=$1667.50. Once the armor has taken more than 32 penetrations, it is actually cheaper to buy a new suit and scrap the old one for metal value (say, 5-10% of original cost). Of course, to get 32 penetration on this corselet requires 32 attacks doing 8 points of damage or more.

Wear, Tear, and Decoration

General wear and tear can damage armor. Armor that is not properly maintained (one hour a week by a skilled craftsman -- see Armor Repair, above) will suffer damage -- effectively, suffering the equivalent of penetrations. Armor that is being actively worn, or is just neglected, will suffer the equivalent of 1 penetration every two months unless it is being actively maintained. This represents accumulated wear on straps, minor breaks and tears, nicks, cuts, and scrapes of all kinds that eventually wear down the armor and require repairs. Penetrations suffered in this manner are treated normally for purposes of enchantment, repair, and optional rules such as DR reduction (see below).

GMs wishing to avoid the bookkeeping of penetrations but who wish to keep track of armor damage can use the wear and tear rule to keep PCs caring for their armor. After any battle in which a character was injured at least once, the armor can be assessed 1d6 penetrations. Modify this roll by -1 or -2 for a small skirmish or melee or by +1 (large battle) to +3 (desperate, huge battle). Penetrations can be assessed on a per-suit or per-location basis. After a Mass Combat, Armor Damage can be assessed normally (after determining the results on the Damage Table) or this simplified system can be used: apply any penalties to survival as a plus to the number of penetrations suffered.

Armor Decoration: Armor may be finely decorated, with precious metals, jewels, or just exceptionally fine construction. Well- decorated armor will cost more to purchase and to repair. Armor decoration is available in fine quality (4x cost) and Very Fine (20x cost, or more). These modifiers will multiply with those of armor quality. At a GM's option, fine decorations may give a +1 to reaction rolls and very fine decorations a +2. Naturally, decorated armor uses its decorated cost to determine cost of repairs . . .

Optional Rules

The following are optional rules that can be added onto the above system. Some of that add even more bookkeeping, and can change the dynamics of combat. All of them have been playtested, but a GM should exercise some caution before using them -- especially the PD reduction rules.

* * *

Sources: GURPS Basic, GURPS Magic, GURPS Ultra Tech, GURPS Robots, GURPS Vehicles.

(Special thanks to Shawn A Fisher, Dan Howard, Bob Huss, and Sean Punch for numerous suggestions and to my players for testing these on their PC's armor.)

Article publication date: September 7, 2001

Copyright © 2001 by Steve Jackson Games. All rights reserved. Pyramid subscribers are permitted to read this article online, or download it and print out a single hardcopy for personal use. Copying this text to any other online system or BBS, or making more than one hardcopy, is strictly prohibited. So please don't. And if you encounter copies of this article elsewhere on the web, please report it to