Strength varies depending on body plan and musculature, but a rough guideline follows the square-cube law: ST equals 2 х the cube root of mass in pounds. (This uses the cube root of mass as a way to get a common “length factor” that doesn’t depend on body plan. Since in GURPS a character’s Basic Lift is proportional to the square of ST, it all works out.)
For a more precise determination of weight (or for huge organisms), divide height (in yards) by two, cube the result, and multiply by 200 to get weight in pounds.