Attribution & Tracking
Blended ROAS & MER Calculator
The Blended ROAS and MER Calculator gives you a single, un-gameable measure of advertising efficiency by dividing your total store revenue by your total marketing spend across every channel. It returns your blended ROAS (the same number as your Marketing Efficiency Ratio), your marketing spend as a percentage of revenue, and, if you supply gross margin, your break-even MER and whether you currently clear it. The result is one source-of-truth metric that cannot be inflated by platforms each claiming the same sale.
Who it's for: DTC operators and finance teams running several paid channels at once who want one blended efficiency number instead of overlapping, double-counted per-platform ROAS.
How the Blended ROAS & MER Calculator works
You enter total revenue for the period, total marketing and ad spend across all channels combined, and optionally your gross margin. Blended ROAS, which is identical to MER, is total revenue divided by total marketing spend. Because the numerator is your actual store revenue and the denominator is every marketing dollar you spent, the same purchase cannot be counted twice the way it is when Meta and Google each take full credit.
The tool also flips that ratio into marketing as a percentage of revenue, sometimes called the cost of acquisition ratio or marketing efficiency from the cost side. It is spend divided by revenue, so a 4.0 MER is the same as spending 25 percent of revenue on marketing. Many operators find the percentage view more intuitive for budgeting because it maps directly onto a profit-and-loss statement.
If you provide gross margin, the calculator computes your break-even MER as 1 divided by gross margin and tells you whether your current MER clears it. A 50 percent margin needs an MER of at least 2.0 to cover product cost and total marketing spend; if your actual MER is above that you are profitable on a blended basis, and if it is below you are losing money overall no matter how strong individual campaigns look.
Use blended ROAS as your top-line efficiency target and per-platform ROAS only for in-channel optimization. Platform ROAS overstates because each system attributes independently and overlaps on shared customers, so adding them together produces a number larger than reality. MER sidesteps that entirely by working from total revenue and total spend, which is why it is the metric most DTC finance teams steer the business by.
The formula
Blended ROAS = MER = total revenue / total marketing spend. Marketing as % of revenue (cost of acquisition ratio) = total marketing spend / total revenue. Break-even MER = 1 / gross margin, and current MER clears break-even when MER is greater than or equal to break-even MER.
Frequently asked questions
What is MER and how is it different from ROAS?+
MER, the Marketing Efficiency Ratio, is total store revenue divided by total marketing spend across all channels, so it measures the efficiency of your entire marketing budget at once. Per-platform ROAS measures a single channel using that platform's own attribution, which overlaps with other platforms and tends to overstate. MER and blended ROAS are the same calculation, and both give you one honest number that platform ROAS cannot.
Why do my platform ROAS numbers add up to more than my blended ROAS?+
Each ad platform attributes conversions independently, so when a customer sees ads on more than one channel before buying, every platform claims that same sale. Summing per-platform reported revenue therefore counts many purchases multiple times, inflating the total. Your store only records each order once, which is why blended ROAS built from total revenue is always the truer figure and usually lower than the sum of the parts.
What is a good MER?+
There is no universal target because the right MER depends entirely on your gross margin: the lower your margin, the higher the MER you need to stay profitable. The most useful benchmark is your own break-even MER, which is 1 divided by gross margin, and you want to run comfortably above it to leave room for overhead and profit. Compare your MER to that floor rather than to a generic industry number.
Should marketing as a percentage of revenue go up or down as I scale?+
Marketing as a percentage of revenue is just the inverse of MER, so a lower percentage means more efficient spend. Many brands accept a higher percentage early on to fund growth and aim to bring it down as repeat purchases and organic demand build. Track it against your break-even point: as long as you stay below the percentage your margin can support, a temporarily higher ratio to drive growth can be a deliberate choice rather than a problem.
What should I include in total marketing spend?+
Include all paid channel spend, such as Meta, Google, TikTok, and any other ad platforms, for a strict ad-only MER. Some teams also fold in agency fees, influencer payments, email and SMS platform costs, and creative production to get a fully loaded view of marketing efficiency. Whichever definition you choose, keep it consistent every period so the trend in your MER is comparable over time.