diff --git a/code/modules/mob/living/carbon/human/species/species.dm b/code/modules/mob/living/carbon/human/species/species.dm
index 25a8149e48..def9ae59f2 100644
--- a/code/modules/mob/living/carbon/human/species/species.dm
+++ b/code/modules/mob/living/carbon/human/species/species.dm
@@ -190,6 +190,7 @@
 
 /datum/species/proc/create_organs(var/mob/living/carbon/human/H) //Handles creation of mob organs.
 
+	H.mob_size = mob_size
 	for(var/obj/item/organ/organ in H.contents)
 		if((organ in H.organs) || (organ in H.internal_organs))
 			qdel(organ)
@@ -249,7 +250,6 @@
 	H.mob_swap_flags = swap_flags
 	H.mob_push_flags = push_flags
 	H.pass_flags = pass_flags
-	H.mob_size = mob_size
 
 /datum/species/proc/handle_death(var/mob/living/carbon/human/H) //Handles any species-specific death events (such as dionaea nymph spawns).
 	return
diff --git a/code/modules/mob/mob_grab.dm b/code/modules/mob/mob_grab.dm
index dde0cef8b2..e40b14dffd 100644
--- a/code/modules/mob/mob_grab.dm
+++ b/code/modules/mob/mob_grab.dm
@@ -372,7 +372,7 @@
 
 //returns the number of size categories between affecting and assailant, rounded. Positive means A is larger than B
 /obj/item/weapon/grab/proc/size_difference(mob/A, mob/B)
-	return round(log(2, A.mob_size/B.mob_size), 1)
+	return mob_size_difference(A.mob_size, B.mob_size)
 
 /obj/item/weapon/grab
 	var/destroying = 0
diff --git a/code/modules/mob/mob_helpers.dm b/code/modules/mob/mob_helpers.dm
index 22da202ede..2f788862f8 100644
--- a/code/modules/mob/mob_helpers.dm
+++ b/code/modules/mob/mob_helpers.dm
@@ -5,6 +5,9 @@
 		return L.mob_size <= MOB_SMALL
 	return 0
 
+//returns the number of size categories between two mob_sizes, rounded. Positive means A is larger than B
+/proc/mob_size_difference(var/mob_size_A, var/mob_size_B)
+	return round(log(2, mob_size_A/mob_size_B), 1)
 
 /proc/istiny(A)
 	if(A && istype(A, /mob/living))
diff --git a/code/modules/organs/organ.dm b/code/modules/organs/organ.dm
index 13eef2eaf4..d8533239e7 100644
--- a/code/modules/organs/organ.dm
+++ b/code/modules/organs/organ.dm
@@ -50,6 +50,7 @@ var/list/organ_cache = list()
 		max_damage = min_broken_damage * 2
 	if(istype(holder))
 		src.owner = holder
+		src.w_class = max(src.w_class + mob_size_difference(holder.mob_size, MOB_MEDIUM), 1) //smaller mobs have smaller organs.
 		species = all_species["Human"]
 		if(holder.dna)
 			dna = holder.dna.Clone()
diff --git a/code/modules/organs/subtypes/standard.dm b/code/modules/organs/subtypes/standard.dm
index 36fc7ba677..d26193c876 100644
--- a/code/modules/organs/subtypes/standard.dm
+++ b/code/modules/organs/subtypes/standard.dm
@@ -2,6 +2,8 @@
 			   ORGAN DEFINES
 ****************************************************/
 
+//Make sure that w_class is set as if the parent mob was medium sized! This is because w_class is adjusted automatically for mob_size in New()
+
 /obj/item/organ/external/chest
 	name = "upper body"
 	organ_tag = BP_TORSO