Heh, not being a Californian, I keep forgetting that there are circumstances in which it may take as long to drive as to bike to work. (In my case, it's about 15 minutes by car, and 35-45 by bike each way.)

And that's a good point about "budgeting" the time for bike riding if you aren't commuting.

Lance Amstrong is not over 60.. flat city and light traffic is not a universal situation.

and as to use of theoretical averages ..
as George Carlin said 'consider the average intelligence of Americans,
and remember half of them are dumber than that'

My commute is about 20 miles round trip, give or take depending on my route.
It takes me 30-40 min to get to work, but 50-60 min to get home (more traffic and uphill). I don't consider it long, but I am used to it. I also don't like tacking on more than an additional 30 minutes to my ride in general (lovely spring/summer days being an exception) because then it cuts into whatever I have going on outside of my ride. It all depends on route or terrain really. More uphill = more time = longer ride, even if it's maybe just adding on another 2 miles.

I do sixteenish miles a day round trip, and sometimes it feels long because I work ten hour days. But I also only work four days a week, and can recover on the weekends.

One thing though, I'm riding a commuter bike and it isn't the ideal ride, but it's comfortable. Come tax time I'd like to buy either a road bike with beefier tires, or a used touring bike.

IMO, this is the best answer. Basing a doable commute on distance as opposed to time doesn't really work for many of us.

For one rider a 10 mile commute could mean a 1/2 hour ride and no big deal. Another rider might do the same ride in an hour and find it exhausting.

My 10.2 mile one way commute is a breeze but a couple of summers ago I had a similar distance commuting in mountainous territory. Between the climbing and the sudden thunderstorms they were two very different commutes in terms of what they took out of me energy wise.

My longest commute was 36 miles one way. I was in pretty good shape at the time and I could do it in about 2 hours. The round trip meant I was on the bike 4 hours minimum a day 3 or 4 times a week. I couldn't do that for more than a 6 month period or so- it just plain wore me out. Over a long term (like year round) of commuting I agree that 45 mins- at a moderate pace- is about the limit.

My daily commute is one mile. (You're jealous, aren't you.) But it was two degrees today (that's Fahrenheit) and dark. The powder wasn't too deep, though--that's good. On freshly plowed roads, I can do about 8-10mph in winter. On snow-covered roads, that speed can easily be cut in half. The primary limiting factor in those conditions is how long you are willing to stay out in the cold. Secondarily, the limiter is how bad the roads are. Distance isn't all that important, but I usually stay within about five miles this time of year.

I have, though, devised a brilliant and scientifically provable formula by which to determine whether a commute qualifies as "long." This is it:

(Bt > (1.5Dt or (Dt + 20m))) = LC

Bt is the amount of time it takes to traverse the commute distance by bicycle, and includes the time it takes to lock up the bike and any additional time that is necessary for changing clothes and the like. Dt is the amount of time required to traverse the commute distance by car, and includes the time required to park and walk from there. m is minutes. LC is a long commute. Therefore, if bicycling takes more than 150% of the time that would be required to drive, then it is a long commute. And if bicycling takes more than 20 additional minutes over the driving commute, then it is a long commute.

The formula does not account for the cost of parking, relative danger, or "cool factor." Otherwise, it is empirically proven and immune to challenge.

For me, I have two choices - cycling or taking the Metro. Both take about the same amount of time (a little more than an hour) so I can't call my bike commute long. And if I had a car, it'd probably take about the same amount of time too, given how bad traffic here is.

There aren't many commutes of any distance in London that would be faster by car, train or bus. And depending on your ability to deal with horrible traffic, claustrophobia and general ******baggery, even a ride home at 11pm in 38 degree wind and rain can be more comfortable than the alternatives.

Like everyone has said, more than 45 min and the average person will start to think about bagging the bike for another option. That is also the point where it might actually be faster, in London anyways, to take motorized transport.

Depends...

In the summer, anything over 25 miles gets long for me. The longest I've gone is 32 miles, but that takes too much time to get up early enough to do it on a regular basis.

In the winter when it's really cold, like below 15F, I have trouble staying warm for anything beyond an hour, so even 15 miles is a long commute.

My commutes are between 35 and 55 minutes. I consider over an hour a long commute.

My commute is about 7.5 miles each way, but I carry clothes and meals for work, and Seattle is quite hilly. I also lose quite some time traversing the entire hospital campus twice on foot to get from the bicycle cage to the bike commuter locker room (shower) and then back to the ER where I work. With that and working 12 hour shifts on my feet I wouldn't want my commute to be much longer. Especially since I am also going to be back in school five days a week and carrying schoolbooks as well.

When I was working "only" 10 hour shifts and not going to school I would've been okay with a little bit longer commute. Sometimes I'm envious of flat landers and I'm definitely envious of those that get to commute out in the country, except on windy days!

tldr version: varies on load, terrain, weather, sleep, type of work you do. Anything over 10 miles each way I think I would feel is "long" unless it was a flat and pleasant commute.

IMHO
Short commute = wear street clothes and not need a shower, no water bottle.
Medium commute = bike clothes and freshen up (not necessarily shower), 1 water bottle.
Long commute = mandatory scrub/shower and serious concerns of extreme weather. Fatigue builds through the week. 2-3 waters.
XL commute = rechargable battery dies before getting home, backup battery or recharge at work needed. Rest days needed during the week. May need stop to refill water bottles. Need to have snack available.

I'm commuting ~10 miles RT for work, four days a week and probably an extra 5 miles for school and other stuff three of those days. If it I wasn't crossing some of the busiest roads in my city I'd probably get from my apartment to work in about 15 minutes, but I spend at least 5 minutes stopped at various lights around town that intersect heavily trafficked roads. In the spring, fall and winter the rides aren't too bad, although riding home at 12am in 20 degree temperatures isn't something most Texans are prepared for. The summers are a totally different monster, once the temperature is hitting 100-105 daily in July my 20-25 minute ride turns into a 25-35 minute ride (I think my hottest ride this summer was 114 a few times) and the heat sucks a ton of energy away. Additionally most of the year I just have to change clothes when I get to work, but from June until mid September extra time has to be allotted so I can stop sweating and get all cleaned up. It takes anywhere from 15 to 30 minutes to get from my apartment to my job via car so I'm not really saving or losing any time by riding.
I think it's all situational, right now I'd have no problem commuting 20-25 miles round trip for work but through June, July and August 20 miles daily might be pushing it in the heat.

Interesting, my commute doesn't fit nicely in any of those categories. I don't drink any water on my commute (usually chug a whole bottle once I arrive though), can cycle for a couple of days in a row in street clothes without chaffing, but need to shower every time. Obviously climate, terrain, and personal differences all affect these things, but it's interesting to note the differences.

It might depend on motivation, as I don't really think of any ride much under 45 minutes to be much of a workout even if I do it twice a day. That's about how long it takes me to ride my 9 hilly miles to where I catch my bus, but if it was shorter I would need to do longer rides home more often than I do now. When I run I rarely run for less than 45 minutes either, though that's only once per day.

New job resulted in a 15 mile each way, one hour commute. Right on the edge of what I'm willing to do.(for me it is a 20 minute car commute). I consider this a long commute.

I think most people here would agree that any 30 mile RT commute is considered to be a long commute, for a daily commute distance.

That's just about an hour of steady cycling each way, for a fit rider!

- Slim

^^^ That's not an upper limit. Plenty of people do more than that, even on a daily basis.

Noted

It is not the miles that I consider, but the time it takes me to cover those miles. Once the commute time is in hours I consider that long. Takes me 20 minutes to go 3 miles. I used to live farther away and took 45 minutes to go 6 miles. Short distance for most here, but sometimes it can feel long.

When it starts to interfere with life, family, works, etc.

When you start to hate being on the bike all the time. That's when it's too long. If I can ride home and still want to hop on the mountain bike for a trail ride, then I'm happy. If all I want to do afterwards is be lazy, then it's too far.