Cum. MER
Whether the day is paying for its ads so far, hour by hour.
What it means
Cum. MER is the running total of Ad Spend divided by the running total of Total Sales, from the first hour of the day up to the row you're on, shown as a percentage. Lower is better: it's the share of the revenue taken so far that went back out on advertising. It's one division of two running totals — never an average of the hourly MER figures above it.
Show the math
Formula and a worked example
Cumulative Ad Spend is Meta plus Google added up from the first hour through this one. Cumulative Sales is Total Sales over exactly the same hours.
It reads as a percentage and lower is better. 25% means a quarter of the money taken so far paid for the advertising.
Worked example. By 12:00 you have spent €400 and taken €1,600, so Cum. MER = 400 ÷ 1,600 = 25%. The 13:00 hour is a poor one on its own — €60 of spend against €120 of sales, an hourly MER of 50%. The running figure barely flinches: 460 ÷ 1,720 = 26.7%.
That damping is the point and the catch. Early rows swing on almost nothing, late rows can hardly be moved, and with no cumulative sales yet the column shows 0 rather than an impossible ratio.
It answers the question
How much of the money taken so far has gone on ads? The running figure answers it at any hour, and by the last row it's the whole range's spend over the whole range's sales — the same measure MERMERWhole-business marketing efficiency across every channel.Under 30% is healthy reports for the period.
Why it matters
It's the one efficiency figure on the tab that doesn't panic. A single hour's MER swings wildly on two or three orders; this one carries every hour behind it, so when it moves, something moved.
It also turns an end-of-period number into a decision you can still make. If the running figure is far above where your days usually settle by mid-afternoon, there are hours of budget left to do something about it.
What good looks like
Cum. MER carries no band of its own. The standard to hold it to is the one published on MER, which the last row of the day lands on — every row above it is the same measure with less data behind it. Early hours are not a verdict: a full morning of delivery and two orders can put this figure anywhere. Treat the first rows as a check that spend is running, and start reading the number as a number once there is enough revenue underneath it to be worth dividing by.
How to improve it
| Lever | What you do | Expect | How long | Watch out for |
|---|---|---|---|---|
| Fast Stop buying the hours that never pay | Use the ad schedule to end delivery in the hours where spend lands and orders don't | The running figure sits lower all day | 1 week | You removed spend rather than winning sales. Total Sales usually falls with it, so read the last row's Cum. Total Sales, not only the ratio. |
| Fast Move budget to the channel carrying the day | Compare the Meta and Google columns against the sales in the same hours, then shift the daily budgets | The same spend against a better running ratio | 1–2 weeks | This table credits a sale to the hour the order was placed, not the hour that earned it, so a channel that works slowly reads worse here than it is. |
| Slow Raise what an order is worth | Work on AOV so the same spend divides into more revenue | The running figure falls without touching a budget | 1 quarter | Bundles and free-delivery thresholds usually buy AOV with margin, so a better ratio here can arrive with a worse Contribution Margin. |
| Slow Fix the site for the hours you're buying | Check that the pages your evening traffic lands on load and convert as well as your morning pages | The same traffic turns into more revenue in the weak hours | 1 quarter | Site work is slow and never appears in an ad account, so the gain is easy to credit to whatever budget change happened the same week. |
Every lever costs something somewhere. The last column is the one to read twice.
Read it with
Efficiency alone can be improved by shrinking. Read it against Cum. Total SalesCum. Total SalesShows how revenue builds through the day. or you can't tell growth from retreat.
Growing and cheaper
More revenue for a smaller share of it spent. The rare corner, and the one worth spending into before the day is out.
Bought the day
Revenue is up and it cost a bigger slice to get. A decision rather than a fault — the question is whether the slice is still one you can live with.
Cheap and quiet
A better ratio on less revenue usually means less advertising, not better advertising. Look at the spend curve before congratulating anyone.
The one to act on
Less revenue and a larger share of it going to ads. Every hour you leave it, the running total gets harder to pull back.
The hourly column tells you which hour turned; the running column tells you whether it mattered. An hour at 60% MER against a day sitting at 24% is noise on a small denominator. The same hour when the running figure has been climbing since 09:00 is a trend with a name.
These two catch the difference between a pacing problem and a performance one. A running ratio holding steady while the spend curve runs ahead of last period means you're buying more of the same thing. A ratio climbing on a flat spend curve means the money is doing less than it was, and no budget change caused it.
Common misreads
It's one division of two running totals. Averaging the hourly figures gives a different and worse answer, because it treats a €20 hour and a €2,000 hour as equals.
0 is what the column shows when there are no cumulative sales to divide by yet. Read it as no data, not as free traffic.
A running total can only move a little once it's carrying a full day. A tick up means the latest hour was worse than the average behind it — check the MER column on that row to see how much worse.
Also called
Cumulative MER · running marketing efficiency · MER to date
See yoursYour running efficiency hour by hour on the Hour tab, beside the spend and revenue curves behind it.
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