How much a creature can lift and carry is determined by its STR and SIZE.
| Amount in Pounds | Effect Upon Hitting Threshold |
|---|---|
| 65 + (20 × STR) | lightly encumbered |
| 130 + (40 × STR) | heavily encumbered |
| 195 + (60 × STR) | Cannot carry anything more |
| Amount in Pounds | Effect Upon Hitting Threshold |
|---|---|
| 60 + (20 × (STR + (SIZE - 5)²)) | lightly encumbered |
| 120 + (40 × (STR + (SIZE - 5)²)) | heavily encumbered |
| 180 + (60 × (STR + (SIZE - 5)²)) | Cannot carry anything more |
A creature may also push, drag, or lift a weight in pounds up to twice their carrying capacity. While pushing or dragging weight in excess of their carrying capacity, the creature's movement speed drops to 5 feet.
Design Note: I have many spreadsheets of algebra to make sure the weight and carrying capacity scaling make physical sense (one has to scale on a power of 2 and the other on a power of 3), fit with our intuitions of strength on the human scale, and also allow creatures to be strong enough to carry their own bodies. It's actually a very limited set of values that that works for.