I can't find this info anywhere. I can only assume it's a dumb question.
When I look at my 100 amp panel I see 32 spots for breakers. Down one side I count 16 and another 16 on the other. There are two 30 amp and 1 60 amp, and then about 20 more 20 amp breakers. When I add it up I get 510 amps. But the panel is just good for 100 amps. So I have to ask - is there a maximum load that can be placed on a 100 amp panel? Or a 200 amp? And why is there only a net increase of 8 spaces - from 32 to 40 - when going from 100 amp to 200 amp - a doubling of capacity?

Also, when I calculate the loads in my house, I am having trouble breaking it up properly. For example, I have a home office with a computer (450 watt power supply), monitor, laser printer, and various plugin low voltage things such as speakers and chargers, etc. So it's cleat that not even a single 20 amp circuit will cover this. 2 would do it unless I want to bring in a 1300 watt space heater which is almost enough on it's own to overload a 15 amp circuit when you add a lamp with two bulbs. So I find myself needing 4 circuits in just that one room. Then there's my girls. They each have computers, curling irons, 1400 watt hair dryers, stereos, TVs, DVD players, satellite boxes, game systems, ceiling fans, space heater, etc. Then my wife and I have a bedroom that has about the same. Then spare bedroom, living room, family room, kitchen, bathrooms, and outside. Add central air, (gas furnace and water heater), electric range, lights. Now I don't think we're unusual. But I don't see how the calculations add up to just 100 amps. The calculations I do show that when my daughters are getting ready for school and my wife for work, while both bathrooms are occupied, the biscuits are in the oven, I'm on the computer and the kids of course have their computers on during the summer, I am exceeding the capacity by a long shot. But so far I have never tripped the main. What am I missing? How the heck does a 1300 watt heater or a 1400 watt hair dryer work on a 15 amp non dedicated circuit at all? I mean, once you add a couple lightbulbs, you are exceeding 1440 watts which is the max for that 14 gauge wire and 15 amp breaker, right? Why doesn't the breaker just trip as soon as you turn on the dryer?
And finally, how do I determine proper capacity - 100 or 200 amp, when the sum of the devices doesn't accurately represent the real usage?
Thanks!

1440 is the max load on a circuit that runs three hours or more. A 15 amp circuit can handle 1800 watts when the load runs less than three hours, which is usually the case for a residential circuit.

Pay no attention to the amount of breakers and how they add up, that is completely irrelevant, as not all the circuits are loaded to 100% and very unlikely all to be running at the same time.

Service calculations are done according to Article 220 in NFPA 70: National Electrical Code®

And illustrated by the Examples in the Annex.

Basically, it is assumed that 3000 watts of load will run at 100%, and the remaining load,and only certain items, is calculated at 35%.

There are other optional methods depending on size of heat and air conditioning loads.

You can try reading through Article 220, but I assure you, to a layperson it will make you run screaming into the night.

If services were calculated by totaling every load in a building, a service for a normal home would need to be 600 amps.

You have noted that even with all your appliances, kids leaving all the lights on, etc. the Main Breaker never tripped.