diff --git a/code/modules/mob/living/carbon/human/human_defense.dm b/code/modules/mob/living/carbon/human/human_defense.dm
index 407b83c9c34..7406c693b53 100644
--- a/code/modules/mob/living/carbon/human/human_defense.dm
+++ b/code/modules/mob/living/carbon/human/human_defense.dm
@@ -84,7 +84,7 @@ emp_act
 
 /mob/living/carbon/human/getarmor(var/def_zone, var/type)
 	var/armorval = 0
-	var/organnum = 0
+	var/total = 0
 
 	if(def_zone)
 		if(isorgan(def_zone))
@@ -94,10 +94,13 @@ emp_act
 		//If a specific bodypart is targetted, check how that bodypart is protected and return the value.
 
 	//If you don't specify a bodypart, it checks ALL your bodyparts for protection, and averages out the values
-	for(var/datum/organ/external/organ in organs)
-		armorval += getarmor_organ(organ, type)
-		organnum++
-	return (armorval/max(organnum, 1))
+	for(var/organ_name in organs_by_name)
+		if (organ_name in organ_rel_size)
+			var/datum/organ/external/organ = organs_by_name[organ_name]
+			var/weight = organ_rel_size[organ_name]
+			armorval += getarmor_organ(organ, type) * weight
+			total += weight
+	return (armorval/max(total, 1))
 
 //this proc returns the Siemens coefficient of electrical resistivity for a particular external organ.
 /mob/living/carbon/human/proc/get_siemens_coefficient_organ(var/datum/organ/external/def_zone)
@@ -117,11 +120,10 @@ emp_act
 /mob/living/carbon/human/proc/getarmor_organ(var/datum/organ/external/def_zone, var/type)
 	if(!type)	return 0
 	var/protection = 0
-	var/list/body_parts = list(head, wear_mask, wear_suit, w_uniform)
-	for(var/bp in body_parts)
-		if(!bp)	continue
-		if(bp && istype(bp ,/obj/item/clothing))
-			var/obj/item/clothing/C = bp
+	var/list/protective_gear = list(head, wear_mask, wear_suit, w_uniform)
+	for(var/gear in protective_gear)
+		if(gear && istype(gear ,/obj/item/clothing))
+			var/obj/item/clothing/C = gear
 			if(C.body_parts_covered & def_zone.body_part)
 				protection += C.armor[type]
 	return protection
diff --git a/code/modules/mob/living/damage_procs.dm b/code/modules/mob/living/damage_procs.dm
index 5431a2775ad..cc76d40c654 100644
--- a/code/modules/mob/living/damage_procs.dm
+++ b/code/modules/mob/living/damage_procs.dm
@@ -52,7 +52,8 @@
 		if(AGONY)
 			halloss += effect // Useful for objects that cause "subdual" damage. PAIN!
 		if(IRRADIATE)
-			radiation += max((((effect - (effect*(getarmor(null, "rad")/100))))/(blocked+1)),0)//Rads auto check armor
+			var/rad_protection = getarmor(null, "rad")/100
+			radiation += max((1-rad_protection)*effect/(blocked+1),0)//Rads auto check armor
 		if(STUTTER)
 			if(status_flags & CANSTUN) // stun is usually associated with stutter
 				stuttering = max(stuttering,(effect/(blocked+1)))
diff --git a/code/modules/mob/mob_helpers.dm b/code/modules/mob/mob_helpers.dm
index ec4bffb2ab1..17f1717f580 100644
--- a/code/modules/mob/mob_helpers.dm
+++ b/code/modules/mob/mob_helpers.dm
@@ -119,8 +119,44 @@ proc/hasorgans(A)
 	return ishuman(A)
 
 /proc/hsl2rgb(h, s, l)
-	return
+	return //TODO: Implement
 
+/*
+	Miss Chance
+*/
+
+//TODO: Integrate defence zones and targeting body parts with the actual organ system, move these into organ definitions.
+
+//The base miss chance for the different defence zones
+var/list/global/base_miss_chance = list(
+	"head" = 40,
+	"chest" = 10,
+	"groin" = 20,
+	"l_leg" = 20,
+	"r_leg" = 20,
+	"l_arm" = 20,
+	"r_arm" = 20,
+	"l_hand" = 50,
+	"r_hand" = 50,
+	"l_foot" = 50,
+	"r_foot" = 50,
+)
+
+//Used to weight organs when an organ is hit randomly (i.e. not a directed, aimed attack).
+//Also used to weight the protection value that armour provides for covering that body part when calculating protection from full-body effects.
+var/list/global/organ_rel_size = list(
+	"head" = 20,
+	"chest" = 40,
+	"groin" = 30,
+	"l_leg" = 30,
+	"r_leg" = 30,
+	"l_arm" = 30,
+	"r_arm" = 30,
+	"l_hand" = 10,
+	"r_hand" = 10,
+	"l_foot" = 10,
+	"r_foot" = 10,
+)
 
 /proc/check_zone(zone)
 	if(!zone)	return "chest"
@@ -142,6 +178,20 @@ proc/hasorgans(A)
 
 	var/ran_zone = zone
 	while (ran_zone == zone)
+		ran_zone = pick ( 
+			organ_rel_size["head"]; "head",
+			organ_rel_size["chest"]; "chest",
+			organ_rel_size["groin"]; "groin",
+			organ_rel_size["l_arm"]; "l_arm",
+			organ_rel_size["r_arm"]; "r_arm",
+			organ_rel_size["l_leg"]; "l_leg",
+			organ_rel_size["r_leg"]; "r_leg",
+			organ_rel_size["l_hand"]; "l_hand",
+			organ_rel_size["r_hand"]; "r_hand",
+			organ_rel_size["l_foot"]; "l_foot",
+			organ_rel_size["r_foot"]; "r_foot",
+		)
+/*
 		ran_zone = pick ( 
 			20; "head",
 			40; "chest",
@@ -155,6 +205,7 @@ proc/hasorgans(A)
 			10; "l_foot",
 			10; "r_foot",
 		)
+*/
 	
 	return ran_zone
 
@@ -167,45 +218,13 @@ proc/hasorgans(A)
 	// you can only miss if your target is standing and not restrained
 	if(!target.buckled && !target.lying)
 		var/miss_chance = 10
-		switch(zone)
-			if("head")
-				miss_chance = 40
-			if("l_leg")
-				miss_chance = 20
-			if("r_leg")
-				miss_chance = 20
-			if("groin")
-				miss_chance = 20
-			if("l_arm")
-				miss_chance = 20
-			if("r_arm")
-				miss_chance = 20
-			if("l_hand")
-				miss_chance = 50
-			if("r_hand")
-				miss_chance = 50
-			if("l_foot")
-				miss_chance = 50
-			if("r_foot")
-				miss_chance = 50
+		if (zone in base_miss_chance)
+			miss_chance = base_miss_chance[zone]
 		miss_chance = max(miss_chance + miss_chance_mod, 0)
 		if(prob(miss_chance))
 			if(prob(70))
 				return null
-			else
-				var/t = rand(1, 11)
-				switch(t)
-					if(1)	return "head"
-					if(2)	return "l_arm"
-					if(3)	return "r_arm"
-					if(4) 	return "chest"
-					if(5) 	return "groin"
-					if(6) 	return "l_foot"
-					if(7)	return "r_foot"
-					if(8)	return "l_hand"
-					if(9)	return "r_hand"
-					if(10)	return "l_leg"
-					if(11)	return "r_leg"
+			return pick(base_miss_chance)
 
 	return zone