Often business owners wish to get an estimate for a website project whether it is for a new site, one that needs pieces added or one that needs a whole makeover. Although there are developers who have used formulas (ie: 10 pages, first page costs $x), it is better to figure out what features the site needs to before getting a quote.
Features you want to think about are:
Allow visitors to buy directly from the site (digital or other products, services, subscription payments, etc.)
Calendar with or without the ability to make appointments
Use of video
Other important pieces of a website project to think about are:
Your budget limits
Who will be working directly with the web developer (the fewer the better)
If you need a new or revamped logo
If you want to be trained to do the maintenance and what parts want to update
If you need more than basic Search Engine Optimization (SEO) such as Google AdWords
If you have Social Media needs.
If you need content to be written for you
If you need to get photography and/or video and if you need photo and video editing
These are just a few areas to have thought about before asking for an estimate. I can often give a ballpark estimate/range in my first meeting.