Hit Points by Size

ize matters, baybeee. Hit points are graded on three axes: size, toughness, and fightiness.

Size determines the number of hit dice.

Toughness determines the size of the hit die.

Fightiness is a Con mod or other multiplier for creatures that are way beefier than they should be, or way less.

The same calculations can be used for both creatures and objects: an axe vs a desk compared to an axe vs a guy is about the same calculation.

Sizes:

Diminutive :: 1 die :: bugs, lizards, desk pens

Tiny :: 2 dice :: cats, toasters, babies

Small :: 4 dice :: children, dogs, an office chair

Medium :: 8 dice :: adults, mo-peds, large goats and small horses

Large :: 16 dice :: bears, tiny cars, a back-yard shed

Huge :: 32 dice :: trucks, elephants, a decently-sized tree

Gargantuan :: 64 dice :: whales, small buildings, heavy construction equipment, big trees

Colossal :: ships, buildings

Toughness:

Wimpy :: 1 hp per die :: regular domesticated animals, humans, fragile or everyday objects (paper, glass, and plastic)

Hardy :: 1d4 :: tough-wearing objects (wood, plastic, rubber), wild animals

Tough :: 1d6 :: hardened objects (thin or brittle metals, hardened rubber), animals known for their armor like badgers, rhinos, and turtles

Hard :: 1d10 :: industrial objects (steel, hardened glass, solid rock)

Invulnerable :: 1d12 :: rebar & concrete, titanium, aerospace ceramics

So what we get are critters like a cat (2 hp), a dude (8 hp), or a bear (16d6 or appx 56 hp). We also see objects like a laptop (2 hp), a bike (4d4 or about 10 hp), and a backhoe (32d10, give or take, or 176 hp). Seems more-or-less correct.

We can adjust within those ranges as needed. Maybe a big truck has 32 hit dice while a smaller pickup has 26 and a compact car has 20. Sure. A giant baloon-animal gets 1 hp because its actual size is diminutive, and it’s inflation alone that makes it a large creature.

Our minimum is 1 for bugs n things, our maximum is around 64d12, or 416, for a building or a cargo ship. With a fireball-style explosive at 8d6 that means an average of 15 fireball-sized charges to take it out (416 / 28 = 14.8). That seems about right. Our outliers are a reinforced mini-drone the size of a mouse 1d12, avg 7 hp), and a pile of jello the size of a mountain (64 hp). The smaller is a mouse that’s as hard to kill as a man; seems okay. The larger is a mountain that takes the same effort to wreck as a grizzly bear; again, that feels right.