Feature Estimation: What is the real cost of adding a feature to a website?

July 25, 2014

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Lets imagine we are the agency supporting a legacy website and we've not worked on it for a while. The client calls and wants a new feature adding. Initial responses are that doesn't sound like a lot of work. For example, lets say the client wants new delivery option adding to the checkout.

The codebase is quite old, without tests or documentation.

Project Manager asks for a time estimate to implement the feature. As it doesn't sound much you immediately reply with a “shouldn't take more than a few hours”.

To give even a reasonable estimate you should take the following into account:

If you have quantifiable answers for all the above you can then estimate the cost of the feature based on the following:

Cost of feature  = ramp-up time (dev server, code familiarity etc) 
                   + initial feature implementation 
                   + testing 
                   + client demo 
                   + implementing client changes * 
                   + testing *
                   + client demo *
                   + Client approval
                   + testing
                   + put live
                   + testing    

    * these steps can be repeated until client is happy.

In the above formula you:

Agile Method

Most of the above is negated if the developer adopts an Agile Workflow. However, this isn't practical when working on inactive projects that are rarely touched. Agile is better for continuously developed projects.

I'd be interested in hearing peoples thoughts and experiences based on the above scenario. Please feel free to tweet me with your comments.