Now, how many hours are you likely to take on the project? To answer this question satisfactorily, you should be detailed. Development time, server set up time, debugging, changes from client, those changes where the client begins "the site is fine i only want to add 'one small change' ", training, travel time and costs, time taken up in meetings with client etc

Once you have some up with the time it will take (in days or in hours) then multiply by how much you are earning right now and you have your figure.