What do you mean?
The fastest way - dwelling coverage = square footage times $175. This works okay for straight tract homes. use $250 for nice home, $350 or higher for custom homes.
I actually recommend gettign some sort of cost estimator. The somewhat standard is Marshall and Swift.
There is no secret formula to do these correctly. There are always 'oh, by the way', such as a built in garage is more expensive than a standard garage. A standalone garage is separate structure, so it doesn't need to be accounted for (as long as there is adequate separate structure coverage), etc.
Of course, keep an eye on the kitchens, and weird things like a in-law apartment above the garage out back. Kitchens are by far the most expensive room in the house. Have your kitchen fully remodeled, then you'll be pretty good at estimating kitchen values
Dan