# How to compare the oil production in barrel vs production in tons

I hope this is the right SE site...I was unsure if to post here or on Physics, but I see there are quite many questions about oil here. So, my question is the following: I would like to compare the huge oil production of Texas, vs the minuscule (in comparison) oil production of a small region in Europe. I know it's silly, but some people are making this comparison and I want to show it's meaningless with actual numbers. Texas oil production is easy to find:

http://www.rrc.state.tx.us/oil-gas/research-and-statistics/production-data/texas-monthly-oil-gas-production/

1 131 557 443 barrels for 2016: I'm a little bit surprised they can pin it down to the single barrel (I guess much more than a barrel is lost in spillage, contamination, etc.), but oh, well.

The European region I'm considering has a production of about 3.75 million tons of oil. So, how do I compare barrels (a unit of volume) to tons (a unit of mass)? For a rough number, I thought oil must be lighter than water, since it floats on it, so if I consider water density, I'll get an upper bound. Now, since an oil barrel seems to correspond to 159 liters according to Wikipedia, I would get an upper bound of $$(1\ 131\ 557\ 443 * 159)/1000\ m^3 * 1 \ ton /m^3 = 179\ 917\ 633 \ tons$$

About 180 million tons of oil (thus the comparison is ridiculous, as I suspected). But oil density is less than water, and it's actually very dependent on the type of oil being extracted, so to get a lower bound I will consider a density of $790 \ kg/m^3$ which I think is fairly low for Texas oil (correct me if I'm wrong). So I get about 142 million tons of oil, and this is still nearly two orders of magnitude larger than 3.75 million tons of oil. Is this correct? Would it be possible to get sharper estimates, or is this the best one could hope to get, given all the uncertainties in this calculation?