to estimate what it costs. The most common is the MSB calculator.
But if you're in an area where you can resale your house for double or triple what you bought it for a couple years ago, then it can probably be rebuilt for less than the current value.
If you're in an area with bad resale value than it's probably going to cost more to rebuild than you bought it for.
Just make sure the insurance company guarantees replacement cost on your home and as long as you're going with a reputable company and you like the rate you'll probably be fine.