Ecommerce MER / Blended ROAS Calculator
Calculate business-wide marketing efficiency from total revenue, paid media spend, and broader marketing costs.
Marketing efficiency
Optional contribution check
Measure marketing efficiency across the whole ecommerce business
Use this calculator when channel-level ROAS is too narrow and you want to compare total business revenue with paid advertising and broader marketing costs.
Blended ROAS compares total revenue with paid media spend. MER goes one step further by comparing revenue with the full marketing spend entered, including non-media costs such as agencies, creative production, and marketing tools.
This makes the calculator useful for higher-level budgeting and for checking whether strong platform ROAS still translates into efficient marketing at the business level.
Businesses use MER and blended ROAS terminology differently. This calculator defines blended ROAS as total revenue divided by paid ad spend and MER as total revenue divided by total marketing spend.
How MER and blended ROAS are calculated
The calculator starts with total business revenue and separates paid media from the rest of your marketing cost structure.
Calculate blended ROAS
Total revenue is divided by paid advertising spend.
Build total marketing spend
Agency fees, creative, marketing software, and other entered marketing costs are added to paid media.
Calculate MER
Total revenue is divided by total marketing spend to measure business-wide marketing efficiency.
Check contribution economics
If a pre-marketing contribution margin is entered, the calculator shows contribution after marketing and the MER where marketing spend would reach break-even.
Example MER and blended ROAS calculation
Suppose an ecommerce business reports the following monthly performance:
Blended ROAS is about 6.67 because $100,000 of revenue is divided by $15,000 of paid media. Total marketing spend is $20,000, so MER is 5.0 and marketing consumes 20% of revenue. With a 40% pre-marketing contribution margin, contribution before marketing is $40,000 and contribution after marketing is $20,000. Break-even MER is 2.5.
What each result means
MER and blended ROAS answer related but different questions about marketing efficiency.
Blended ROAS
Total revenue divided by paid advertising spend. It gives a business-wide revenue-to-media-spend ratio.
MER
Total revenue divided by total marketing spend entered. It includes non-media costs and therefore can be lower than blended ROAS.
Marketing spend as a share of revenue
The percentage of revenue consumed by all marketing costs entered. It is mathematically the inverse of MER when expressed as a percentage.
Contribution after marketing
Pre-marketing contribution minus total marketing spend. This is available only when a contribution margin is entered.
Break-even MER
The MER where all pre-marketing contribution would be consumed by marketing spend under the contribution-margin assumption entered.
MER and blended ROAS questions
Common questions about business-wide ecommerce marketing efficiency.
What is the difference between MER and blended ROAS?
In this calculator, blended ROAS uses paid advertising spend only, while MER uses total marketing spend including any agency, creative, software, or other marketing costs you enter.
Why can platform ROAS be higher than blended ROAS?
Platform ROAS usually uses revenue attributed by one advertising platform. Blended ROAS compares total business revenue with total paid media, so it does not rely on one platform's attribution model.
Should email software and retention costs be included in MER?
Include them if your goal is to measure the full marketing cost structure consistently. Leave them out if you are intentionally measuring a narrower acquisition-only definition.
What is a good MER?
There is no universal target. Sustainable MER depends on contribution margin, fixed costs, growth goals, and how broadly marketing spend is defined.
Why add contribution margin to an MER calculation?
Revenue efficiency alone does not show profitability. Contribution margin indicates how much revenue is economically available to fund marketing before the business reaches break-even.