How many gallons is this keg

I just bought a keg today. It's dimensions are 21" high, 15" diameter, and 51" circumference. I'm pretty sure that it's a 13 gallon. It was smaller than the 15 gl but, that one had extra plastic/rubber on the bottom and top.

Picked it up from a scrap yard. Apparently it's been there for 10 years (I wonder what's inside). I'm switching from extract to all grain and it's been difficult to find kegs. It's aluminum which isn't ideal but it was only 30 bucks. The guy also has some of the more barrel shaped ones in stainless but they also seemed kinda small.

Pics?

volume = 3.14 X radius(squared) X height

arturo7 said:

volume = 3.14 X radius(squared) X height

Click to expand...

This will give you cubic inches. Multiply by .004329 to get gallons from cubic inches

yea looks like 13 according to the math and chart when i adjust for the extra space for the handles.

I can't figure out how to attach pics sorry.

Its probably a 50L (13.2 gal). Very common size from European breweries.