Is their a set formula for time down and time up?

I've noticed at 30-40 feet I stay down longer if I'm up at least 2 min., 40'+ 3min. minimum, yet anything shallower than 30' I can go up gulp and go down without much of a difference in my down time

For deeper dives you need a longer surface interval. It is useles IMO to adhere to a formula becasue so much depends on sea conditions ie, current if you're trying to stay in a particular spot, even visibility can affect you psychologically. Also how your body is functioning on a given day.

I find that excitement, such as when spotting a large fish but having to go up for a second attempt, will increase the surface interval. The key is always how fast you can achieve a relaxed state after a dive.

In shallower depths there isn't an element of risk and I believe this is a contributing factor to being able to relax faster. Therefore being able to make another dive quicker. I don't know that it would translate into the same bottom time though. The bottom line is that the better your breath up the longer your bottom time will be regardless of the depth.

Weighing is an important factor for me. If I'm too bouyant in shallow water it will negatively affect my bottom time.

I say stay away from formulas and computers and focus instead on what you feel. I believe this to be the way to become a better diver.

2 to 3 times your down time is a good surface interval, the longer the better but I rarely follow this unless I'm doin' scary stuff.

...even visibility can affect you psychologically...

I just had this experience recently and agree 100%

2 to 3 times your down time is a good surface interval, the longer the better but I rarely follow this unless I'm doin' scary stuff.

I thought I'd heard this someplace before and seems I've been <> following this guideline.

I say stay away from formulas and computers and focus instead on what you feel. I believe this to be the way to become a better diver.

I would agree with focus on how you feel as a guide to come up, but not as a guide to go down.

Sorry if I sound like a broken record and I know I've said this a lot before, but its uncanny how many people have the same experience I did when I first got my D3. If I waited until I felt totally recovered and ready to dive, I found that I has a surface interval of around 45 seconds. It seems like everyone is around 45 seconds. That isn't long enough for your tissues to replenish oxygen. I look at the damn watch to make sure my surface interval is long enough.

Or lets say I have a fish tied up in kelp at a depth that is a real challenge for me. I know I should take a very long surface interval, maybe 5 minutes, but how can I tell how long it is? My mind may wander as I see fish go by, think about my girl friend, think about my wife, or think about what will happen if my wife finds out about my girl friend. And when my mind comes back to the task, I don't know whether I've been up for 2 minutes or 5 minutes.

Or how about diving in murky water where I can't see the surface. I can't tell for sure whether I went to 30 feet or 50 feet without the D3, and it matters. I should start up feeling a bit fresher if I'm at 50.

I think listening to your body is over rated.

Edit: oh shit, I forgot that this was Pargo in disguise.

2 minutes seems to work well for me. Like Bill said, if I anticpate a deep or difficult dive, I will spend an extra minute or two on the surface. The same applies after I complete one of those dives too.