Rules Of Thumb For Estimating Web App Hours [closed]

Question

We all know that software estimation is difficult to get exact, but I am not looking for exact. I'm looking to be able to derive an approximate number of person-hours for a project to know how many people to hire in a startup.

So, assuming you have:

• A web application built on the .NET platform (C#, ASP MVC, etc...)
• A defined number of use cases with a mix of easy and complex ones (in this project, 70 use cases; but assume a project with a high enough number of use cases to give a good bell curve of complex and not complex)
• A defined database schema (again, in this case there are 50 or so tables, but assume a web application that does more than the typical book example with seven tables :) )
• A partner who wants a quick-and-dirty, best-current-guess estimate, and understands it's not a contract to hold, is experienced with software development, and that the software (and understanding thereof) will version and evolve
• A pool of solid, skilled developers

Do people have any rules of thumb they use to quickly guesstimate the number of hours involved?

UPDATE: I am asking for ballpark estimations rules based on measurable but coarse requirements. Answers of "4 to 6 weeks" are fun, glib answers, but I'd like to hear from people who've actually established some simple barometers of work.

Answer 1

I always write up a detailed list of tasks that I need to accomplish. From there, I can better judge the amount of time for those individual tasks and I add those numbers up. After that, I tack on 25-50% extra as a buffer in case of complications, which always seem to come up.

When I say a list of tasks, I mean something like this: (this is an example, be as verbose as humanly possible, especially on a site-map)

• Database
  • Tables
  • Views
  • Stored Procedures
• Sitemap
  • Home Page
  • About Page
  • Contact Form
• Migration from Development to Production
  • Self-testing
  • Customer-testing
  • Bug-fixing

I always estimate times in terms of hours. (not 15-30 minute blocks)