Giant Snake!

Actually, not a snake, more like a serpentine dragon.

Inspired by the recent news stories about titanoboa and seeking vile beasties to threaten my players with (and sometimes their characters too) I've been concocting a few serpents.

My query is a very quick on about size.

I've got a 20' foot snake like beast and a 30' serpentine dragon type beast.
What size should they be?

Titanoboa is 45' long and wide enough to swallow a human without much effort. How big is that size wise?

Size is based on Mass. First you need to work out how much your snake weighs, then compare to Size.
(Excuse metric units here, makes the calculation easier).
A long-used metric in reptile allometry is that the mass (M in g) of a snake is exponentially related to its total length (TL, in cm):
M = 3.6 x 10[sup]-4[/sup]TL[sup]3.02[/sup]
Note that this is for 'averagely proportioned' snakes. Decrease the 3.6 for fatter snakes, increase it for gracile ones.
Your 610 cm snake (=20') is therefore about 93 kg. A 914 cm snake (=30') is 315 kg
Keeping with the idea that a creature of Size +0 is 70kg, you get this table

Size weight -1 32.5 kg 0 70 kg +1 151 kg +2 324.9 kg +3 700 kg +4 1508 kg
So at 20', a snake would be Size 0, and the 30' snake is pretty much Size +2. However, a serpentine dragon is probably much heavier than a snake: the largest Nile crocodile was 6.45 m (=21') and weighed 1090kg, putting it at Size +3 to +4. You could easily go up to Size +3 without too much of a stretch.

Hope this provides some perspective.

Mark

I agree with Mark: it depends if they are slender or chubby snakes.