A lot of this depends on what you're selling, and your conversion rate (which will depend on exactly how you got those subscriptions).
Is the newsletter geared towards database administrators, who gave you their email address because they wanted to be notified about new developments in their database of choice? Your conversion rate for a database-related product will probably be high, while conversions for a whitepaper on writing your own ebook might not be.
How did you get the subscribers? Are the products you're trying to sell geared towards their niche?
If all you want is a mathematical formula, I like to take a pessimistic approach like so:
Comments
A lot of this depends on what you're selling, and your conversion rate (which will depend on exactly how you got those subscriptions).
Is the newsletter geared towards database administrators, who gave you their email address because they wanted to be notified about new developments in their database of choice? Your conversion rate for a database-related product will probably be high, while conversions for a whitepaper on writing your own ebook might not be.
How did you get the subscribers? Are the products you're trying to sell geared towards their niche?
If all you want is a mathematical formula, I like to take a pessimistic approach like so:
subscribers * 0.25% conversion rate * cost of product = revenue
If it's ads in your newsletter - I have no idea.