This is really a good topic and will really help others. I think you have to examine your previous data before and after doing comparison of current and previous situation you can calculate your sales from site but this will also not show the exact condition. You can just assume figures from this process.
For a website, I would estimate the traffic you expect to see from each channel, and then assume you convert 2 to 5% into sales. From there, estimate the average $ sale per conversion, and you have your revenue model Although, you might start with a low conversion rate and assume it grows over time.
I am still head scratching over one particular section of my business plan.
Am trying to estimate the number of sales each year through each channel of my marketing activity.
Example, how does one estimate the number of potential online sales though website alone?
The number through social media channels eg Facebook business page,twitter?
The number of sales thorugh various magazines online/printed?
How do you convert the number of clicks /readers/twitters in to sales?
Are there ratios/formulas?
I would be immensley grateful for all advise offered.
Sounds like a reasonable guess is where you might start. There are so many variables, it's near impossible to figure unless you have some stats.
Do you plan to pepper spray the entire array of social media? Or are you going to start with one channel, get that up and running well, develop some stats and strategies around that before moving on to the next?
Look at a business similar to yours and ask some questions.
Wow thats actually a really difficult thing to do, as it would highly depend on the traffic that your website attracts. And most SEO experts cant assure you specific results in a specific time frame just because the search engines may change several things along the way that could effect your efforts.