Hi Calvin, there is little or no correlation between the service amperage and the total amperage of the breakers, 200 amps should be fine as the assumption is that not all the circuits would be drawing the max all at the same time.
Electrical service size is based on calculated demand (demand factor). I created a simple Residential Electrical Service Size calculator that is free to download from my website (BestInspectors.Net).
I originally created the calculator to use in my electrical classes for electricians but it went into more detail than we need as home inspectors so I simplified it for my home inspector classes. If you have a question of whether an electrical service is large enough, all you have to do is answer basic questions about the house. The calculator will tell you the service size required (standard breaker size), the size of the service conductors, and conduit size. You can find the calculator in the “Free Stuff for Members area” http://www.bestinspectors.net/members.htm
For an idea of why we do not go by the connected load, think of heating and cooling equipment. We call those “non-coincident loads” because you would typically run one or the other but not both at the same time. Therefore, it is not necessary to size an electrical service to handle running both at the same time. That’s the basic idea behind a calculated demand (aka demand factor).
Keep in mind that this is a teaching calculator and it is based on the NEC. The results are close to 100% accurate but in the event your results are borderline, I recommend having someone who is experienced at sizing electrical services do the calculations. It should be noted that it is common for local rules to deviate from the NEC. For example, some jurisdictions, use either Watts or VA exclusively (not both). The NEC has historically used both. The differences between Watts and VA are usually minimal in houses (I have a separate calculator for that). They might also have wattage schedules instead of using the NEC’s square footage method.