This guide explains what email ROI actually means, how to calculate it honestly, where the return usually comes from, what quietly drags it down and how to decide between doing it yourself and hiring help.Return on investment compares what email earns with what it costs. The basic formula is simple: take the revenue attributed to email, subtract the total cost of running it, divide by that cost and multiply by 100 to get a percentage. If you spent $1,000 and email brought in $4,000 of attributable revenue, your net return is $3,000, or 300 percent of cost.Email is often cheap compared with paid channels, because you are not paying for each visitor. But the figure only means something if you track it properly and count every cost. A tool that costs $30 a month looks cheap until you add the hours spent writing, designing and reporting.