It's a good question, and a hard one to answer. I'll say that you shouldn't just produce marketing activity/materials that cater only for the end of your sales funnel i.e. the conversion. You need to create content that caters to every stage of the buying continuum , so you gradually guide the customer towards purchase in a decent time. I guess I should give an example: You are a software company. You create a white paper on business software efficiencies and produce a landing page for it that allows download of white paper if users enter their email address, opting in to your email list. The return on investment here is how many downloads/opt ins you get. You eventually get 100 opt-ins. Your aim is to eventually sell them one of two products: a CRM or warehouse management system. You create regular emails on these two subjects, and using analytics you start to identify who in the list of 100 is interested in CRMs (based on open and click rates etc) and who are interested in warehouse management. You can then segregate the list into two in order to send appropriate content to each sub-list. The ROI here is how many you've management to move to a sublist. You create an online webinar on the subject of CRMS. You promote it to the CRM sublist. The ROI here is how many sign ups to the webinar you've had. You then target those who watched the webinar by offering them a discount on an entry level service, e.g. preliminary review of current CRM. ROI here is the number of customers who took up review offer. Based on outcome of preliminary review, sell CRM. ROI is revenue. It's a very crude example, but the point is ROI isn't necessarily a sale. You need to produce content of value to guide them towards a purchase. More on reddit.com

The correct answer: A = Average total sales with advertising B = Average Cost of Advertising C = Average total sales without advertising ROI = A - B - C A, B, and C must be monthly averages, ideally six months minimum, and must be same time period. This only works if nothing changed at the organization in that time period. If they added a location or sales staff, you have to take that into account. But that’s just fractions - you have to subtract new sales team members closed sales, and if it’s a company that added a new location (like a restaurant) you have to adjust. Advertising should always pay for itself plus an amount equal to what was spent. At bare minimum. For smaller organizations, the numbers are screwy. If you get a return of +20% and you’re a really small brand with a small budget, be happy. Some small businesses however can grow wildly due to great creative, timing, and market need. More on reddit.com

Analytics, similarweb etc.

More on reddit.com

People who do affiliate marketing ... your roi like ... A community to discuss Affiliate marketing (AM,) paid traffic, SEO, email marketing, and more. READ OUR WIKI: https://reddit.com/r/Affiliatemarketing/wiki/index ... This sub is not for advertisements! Questions and answers about starting, owning, and growing a small business only. ... Topics related to Pay-per-Click (PPC) & other digital ads such as ... More on reddit.com