MER calculator

It adds every marketing cost you enter into one total, divides the period's revenue by that total, and reports the result as a ratio. A MER of 4.4 means the store earned 4.4 dollars for every dollar it spent on marketing in the period. The same total is shown as a share of revenue, which is the number a finance lead usually asks for, and divided by new customers to give a blended acquisition cost that no single platform can flatter.

Revenue comes from the store's order data for the period, stated consistently: net of discounts, and either before or after returns, the same way every month. Google covers Search, Shopping and Performance Max. Paid social covers Meta and any other social platform. Other marketing costs is where most stores under-count: agency fees, feed tools, review and email platforms, affiliate commissions and product sent to creators are all marketing spend. New customers is the count of first-time buyers in the period from the platform, not the count the ad platforms report.

There is no universal good MER. The useful comparison is with your own break-even MER, which comes from gross margin: a store keeping 40 cents of each revenue dollar after product and fulfilment breaks even at a MER of 2.5. Read the ratio next to new customer count each month. A rising MER with falling new customers usually means the store has stopped acquiring and is living on repeat revenue, which feels efficient until it runs out.