Ask a licensed contractor (a few of them), get an idea of the materials your home requires to rebuild. How's the quality of the construction...are you using high quality materials or normal grade? What are the labor costs in the area? Depending on alot of factors, you're looking at $150-$350 per sqft.
The insurance company will use what they call Marshall and Swift calculations http://www.marshallswift.com which is their basis for construction costs.
Again, get with someone that is familiar with construction costs and rebuilding and match it with the insurance company.