Location based pricing based on Lot Size Database : Whats the best way to do thi

[ Moderator note: moved to How-to and Troubleshooting. ]

I have a challenge I’m trying to determine the best way to go about it. Here is the scenario:

1. Client is a lawn care company
3. Client has database of 1.2 million customers
3. Client has database of lot sizes tied to the regions

We need the user to be able to put in their address and the system determine their lot size and then provide a quote. All data is in the database – The database has quotes tied to lot sizes.

I’m wondering the best way to do this. Anyones input is welcomed. I’m thinking gravity forms or formidable would be suitable to accomplish this but wondering if anyone has any thoughts or directions before I start.