My homebrew system uses a slot-based approach. It’s based on B/X D&D, so it should be applicable to that and other editions. See below for a summary. The way it works is the character sheets have lists for carrying, containers, etc. If an item takes a slot, you write it on a line. If it takes two (or more), you write it big across multiple lines. Taking an item out of a container requires an action (and the player would erase the item from the container and write it in the carried section of their sheet).
Carrying capacity: Is 6 + Strength modifier. Carried items are in located sheathes, belt pouches, or strapped to the character’s body. They may also be held in the character’s hands (“equipped”).
Equipped items: Are held in hands or worn (for armor and shields). Some equipped items require a different number of slots to use than to hold (e.g., a longbow requires 1 slot but takes two hands to shoot).
Containers: Hold items and provide expanded capacity. Items in containers do not count against carrying capacity.
- Money pouch: Holds 1 slot (or up to 100 small items). Every character has one. The money pouch does not count against carry capacity. If a character has multiple, only one does not count.
- Backpacks: A standard backpack takes one slot and has 4 slots of storage, an expand backpack takes 2 slots and has 8 slots of storage.
- Sacks: Small sacks have 2 slots and large sacks have 6. A small sack requires one slot when equipped, 1 slot to carry empty, or 2 slots to carry with contents. A large slot requires 2 slots when equipped, 1 slot to carry empty, and 6 slots to carry with contents.
Determining Slots
One hand: Takes 1 slot. If an item can be held comfortably in one hand without help or accessories (such as a hook or string to dangle the item).
Two hand: Takes 2 slots. As above except the item requires two hands.
More hands: Takes 2 slots per person required to comfortably lift and move the item.
Small: Takes no slots if stored in a container or 1 slot otherwise. 100 small items in a container take 1 slot. If an item can be grasped between the forefinger and thumb without help or accessories.
Encumbrance Effects
Going past your limit reduces your speed by 25%. For every two slots carried beyond your limit, it is reduced another 25%.
- 6+STR to 8+STR: 25% reduction
- 8+STR to 10+STR: 50% reduction
- 10+STR to 12+STR: 75% reduction
- 12+STR or more: 100% reduction (no movement).
In 5e, you should probably have disadvantage on ability checks, attack rolls, and saving throws that use Strength, Dexterity, or Constitution when your speed is, e.g., reduced by 50% or more. In 3e, each reduction would increase your armor check penalty by 2 (−2 @ 25%, −4 @ 50%, −6 @ 75%, −8 @ 100%). Apply penalties for other systems as appropriate.