.....climbing per mile? I was just wondering 'cause today we did 48.3 mi. and 3800 ft. of climbing and while it was not overwhelming I found myself really tired post-ride. Other rides haven't left me feeling so worn.

" ... rule of thumb for..... .....climbing per mile? .."

Yes, the rule of thumb is that if you live in a hilly area, you can climb a lot. If you live in a flat area, not so much.

I think over 100' per mile is a hilly ride. You were almost there so I can understand why you're feeling it!

My club's ride difficulty rating scale (based on average elevation gain in feet per mile of a loop ride):
0-25 = flat
25-50 = rolling
50-75 = moderate hills
75-100 = hilly
100+ = mountainous

We don't take steepness into consideration, though if the ride includes a long steep climb, that is pointed out in the ride description.

We do have 100 mile rides with more than 10,000 feet of climbing.
We also have 100 mile rides with less than 2500 feet of climbing (though this is hard to do around here).

I can ride 60 miles and not get above 400 feet. Ill trade gladly with you. any day of the week

I use the Paris-Brest-Paris as a comparison. The 1200 km Paris-Brest-Paris route has approx. 32,000 ft of climbing ... and I found that fairly challenging.

Therefore a comparable 100 km route would have approx. 2666 ft of climbing (32,000/12).

If a 100 km route has more than that amount of climbing ... then it is a hilly route.

We did a 100 km route a few months ago with something in the neighbourhood of 5000 ft of climbing, and I found that extremely challenging. I wasn't sure I was going to make it at a few points along the way.

Mixing feet and KM is confusing. Your 100km ride is about 62 miles or about 80 feet/mile which fits well into the scale posted above as "hilly".

That's a pretty reasonable rule of thumb.

You can have a rule for what qualifies for hilly but it has little to do with how tired you'll feel after finishing the ride. If you do a very 'hilly' ride at 70% of your threshold power it won't feel much, if any, different than a ride on the flats at 70%. Conversely, climbing for 40-60 min at threshold up a steep hill isn't any harder than a 40-60 min TT on the flats.

That's about what I always used. Could be a common outlook for those of us who ride a lot in NorCal.

I usually agree with you but these theories aren't the same as reality for most of us. For example, no matter how hard I go on flats I can always back off and just spin along to the finish once I am tired. I may not be able to hang on to the fast group but I can cruise in.
Now, on a difficult mountain ride it is sometimes a struggle in my lowest gear just to get over those last hills. There is no thought of threshold power, just survival.

I've done hundreds of long rides and there is no comparison between a flat century and one with 10,000 feet of climbing.

thats pretty it. Personally, I find long climbs with steady grades are easier than rollers with a bunch short steep climbs.

Undoubtedly, the problem is worse the bigger you are when riding in a group with lighter riders. I was really thinking about the effort over a given time, not distance.

Just wanted to give you some crap.

^^this is about the average for riding here in the mountains. some more, some less. depends on where you live I guess

Machka's original statement involve Paris-Brest-Paris which is 32,000 feet of climbing over 1200km. Switching that to all-English units and you get 32,000 feet of climbing over 1200*0.625 = 750 miles.

32000 / 750 = 42.6 feet / mile, not 80.

I was referring to the 100km ride she mentioned with 5,000 feet of climbing not the PBP part.

Yep!

Yeah, 100 feet per mile is pretty much the standard. Anything under 80 isn't really worth mentioning.

And yes, a flat ride can be harder than a hilly ride if the intensity is higher.