It's not always given or easily found. Daiwa has #s posted on their site. Penn is hit or miss. You might just ask about a specific model, as someone on this site has probably done a test on a rainy weekend using dogs, trucks, freeweights, or heavyset pals.
The easiest way of getting some idea is looking at the reels line capacity reccomendations. Like 20lb= 350yards.
30lb= 275 yards
40lb=200 yards etc.
Then going at this reccomended line weights and get started at 25%-35%. That is like I was saying the easiest way of interpreting the reels line classes to obviously then it would have that lines drag capacity. OF COURSE THIS IS TOO EASY AND NOT EXACT SCIENCE !!, ALSO THE ROD AND THE HUMIDITY ETC. will affect our drags, ( +/- .006% , HARDY HARR HARR) TOO MUCH BULLONEY to even figure. Forget The HUMIDITY CALCULATORS and all that : except pull on it and tighten the drag "until you think the line is 'starting' to stretch - then "YOUR THERE !!" that is the exact way of setting the guy next to me's drag, and get away if he looses a fish !!!
Does anyone other than me think that the drag ratings are not that important? First of all, I try NOT to push my reels to the limit. However, I do like a reel that performs well in that line class. For this reason, if I am going to over-test for a reel, I expect adequate performance for the overtest. For instance, if I fish 40# on a Torium 20 (designed for 30#, right?), I expect to get a solid 10# of drag out of the reel and want it to button down to around 12# or more. The Toriums will put out a little more than this. do I fish it at 12#? NO! NOT A CHANCE. But I do fish it at 10# and know how to put my thumb on the spool when needed. Generally, I see people fishing stoopid tight drags retying their lines too often. SIDEBAR--Amberjack DO need an extra special tight drag, but most people that fish them seriously use larger reels that are made for drag ranges above 25# (lever reels).
If a new reel comes out on the market and it doesn't say any information about the drag's capacity and there's noone to ask, That reel doesn't seem too good of a definite choice, when you can find one with detailed specifications, etc. about it from the mfgr. No way will some everyday guy 'guess' very well and buy it without some learned information. I can't tell by looking at a picture advertisement of a reel and figure out how much line and what is the max drag. Unless some hands-on out of the box or experience and studying some websites feedback before I'd be KNOWING that stuff. Old timers need to think that there's a starting point for some guys and they don't have nearly the same knowledge and experience as what one may take for granted. They want to get it, just as this man is doing here on this web-post . You may need a lisence to fish but there is not a test that you have to pass to get one, just buy a lisence, What does that tell you?