How large is a small? Or how small is a large?

While difficulty and terrain ranking for caches are quite difficult to determine, limits for cache sizes are explicit stated in the guidelines:

Micro	< 100 ml
Small	100 ml - 1 l
Regular	1 l - 20 l
Large	> 20 l

So we can say the size of a small is somewhere between 100 and 1000 ml. But what number can we put to a large? When

I put the points between the sizes on a graph. These are the red dots. It's impossible to put a straight line though it. But a power curve seems to fit very well. For those who are interested, the formula is:

 y = 0.0002889774 ⋅ x^8.896249

We can enter the numbers fore the sizes. This gives:

Micro	0.29 ml
Small	140 ml
Regular	5.0 l
Large	66 l

For your information: The size of a photo cannister is about 50 ml, an 30 cal ammo box is 3.5 litres a 50 cal 7.5 litres.