Yes, I fully expect this to consist mostly of anecdotes, as I doubt any studies have been done, but I’m wondering whether it’d be beneficial for me to hit the gym early (around 7:30-8am) or at night (around 7pm)?
It’s my experience that they are FAR busier at night. Most people don’t want to get up an hour or more earlier and then get dressed at the gym before work. They would rather go after.
Ditto on what Smitty said.
In my experience, not only are they less busy in the morning, the percentage of serious trainers is higher which means you have way fewer idiots to deal with.
My gym is always busiest after work. Especially on Mondays when people are feeling guilty about the weekend.
The Y I go to is way, way busier in the evening, as swimming lessons are from 4:00 - 7:00 so everyone comes at that time.
The base gym is busier at lunch and in the mornings, because that’s when they are used to working out.
So it depends, but most gyms would be busier at night.
My experience is that they tend to be busy in the morning before work hours (i.e., about opening time to ~7:30-8 am), and very busy in the evening after work hours end (~4:30 - 7 pm). There’s usually another briefly crowded period around lunch hour if the gym is near any work offices.
They’re usually not very busy at all later in the evening, up until closing.
When I first joined my gym (Excel in Anderson,) I asked what the busiest time was. The busiest time, I was told, is 6:00 am to 8:30am. Office workers hit the gym before work, and third-shifters come in after work. It’s also pretty full from 4:00 pm to 6:00 pm. The busiest month is January, before the New Year resolutions fizzle out. 
The gym I go to at home (los angeles) is generally busiest at from noon-1pm and then 5pm onwards. It’s in an office park, so I think most people are coming in during lunch or after work. However, I don’t ever actually been there early in the morning, so it could be busy then too.
Since I generally have nothing to do at home, I go midmorning, when it’s like a ghost town 
At the two gyms that I frequent, busier in the morning, busiest around 3-6pm, and pretty calm after 8pm.
It’s like work vs happy hour. The serious go in the morning. The meat market happens in the evening. Pros are there during both.
I never understood this attitude. It’s not that hard to get dressed at the gym. You need a shower in the morning anyway, so by working out in the morning you save the extra shower you would otherwise need. And best of all, for most people, unforeseen problems and delays during the workday almost never mean you have to skip your workout later.
More difficult than you’d think for a lot of people. Most people aren’t morning people and wake up to go to work out of necessity. Waking up to go work out by choice is more difficult. An extra hour of sleep in a nice warm bed vs. exercise is rough for a lot of people.
And for the business people, transporting office clothes without wrinkling them to the gym can be a challenge. As well as storing them in a tiny locker. And transporting all your toiletries that you use every morning in the privacy of your own bathroom to the gym community counter is challenging. You’d have to be a pretty low maintenance person to pull it off. Most people aren’t and therefore go after work.
Indeed. I’m not going to shave at the gym, and if I have to wear anything above business casual clothing it’ll be rumpled from the lockers, no matter how carefully I hang them in there. Plus, if I’m going to a business meeting, I’d rather not smell vaguely of cologne and chlorinated pool water.
Not that it matters, since my half-awake brain is smart enough to know that if the alarm gets snoozed 'till I miss the workout opportunity time, then the brain gets to sleep a little longer, no matter what I might have planned to the contrary. My half-awake brain is a bit of a tosser, really.
I suppose I’m spoiled in that regard, as I needn’t wear suits, and my gym supplies towels, shampoo, and soap as well as lockers that are plenty large enough to hang good clothes in. Many of the members do wear suits to work, and they manage fine.
Biggest crowds were always after work, Monday through Thursday… with decreasing numbers as the week progressed, with a slight spike on Saturday mornings. Friday nights were deserted, Sundays pretty empty. Early mornings were always the same crowd until about 7:30am when the retirees began to show up.
When I belonged to L.A. Fitness in Pasadena, it was at night 5-8:30
Now at my downtown gym it’s still 5-7 and the one time I went, I had no problem getting on a machine. However, even the 2nd busiest time, noon, it’s very easy to get on a machine. They have some crazy number of ellipticals.
However, the situation is somewhat unique in that this used to be a very rundown location that they recently refurbished into a high-end gym. I’ve seen the morning crowd growing as more and more people here that it’s extremely nice now. I still don’t see it being terribly busy in the morning except between 8 and 9, only because so many people continue to drive into downtown.
I actually go in the morning to see my trainer and noon for cardio.