Size

Size is a more or less hidden item stat, it is never displayed in the game interface can only be accessed through the editor. The only time size is checked is when you put things into the car trunk in Fallout 2, all other containers are limited by weight.

Below is an incomplete list of item sizes. I left out all the quest items of which you have usually only one.

0

All ammo, food, most drugs, containers (bag and backpack), urn, key ring.

1

Super Stimpaks, most miscellaneous items, knife, switchblade.

2

Every weapon using the pistol animation, combat knife, ripper, club, cattle prod, every weapon using the unarmed skill.

3

Every weapon using the SMG animation except the .223 pistol, shotgun, crowbar, super toolkit.

4

Rifles, .223 pistol, spears, sledge and Super Sledge.

5

All kinds of assault rifles, energy rifles, and the Gauss rifle.

6

Big guns.

7

Leather jacket and combat leather jacket.

10

Leather, metal, Tesla, and combat armor.

11

Brotherhood armor.

15

Power Armor and Advanced Power Armor.

The car trunk has an initial capacity of 250. As far as I know, getting the upgrade in New Reno doubles this amount.