Actual Tire width of 37 Inch tires

[D2procon]

I'm looking to pull the trigger and finally upgrade my stock tires to 37 inch tires on stock wheel. Stock tires have a width roughly 12.8 inches and Im trying to get as close to that as I can. Right now I see only options 12.5 vs 13.5. While those are reported width. Are there any tires that are actually over stated than 12.5 or understated than actual 13.5? I cant find any data on this. All I see are actual tire dimaters but nothing on width. Any recommendations?