Predict Your Email Marketing Profits with My Ecommerce Napkin Math Formula!
Let’s not waste time. If you’re an ecommerce brand and you’re guessing how much revenue your email marketing will generate this month, you’re not serious about your business.
I’m going to give you a napkin math formula — the same one I use with 7-, 8-, even 9-figure brands — to accurately forecast how much your email campaigns are going to bring in.
No more sending emails and hoping they work.
You’ll know BEFORE you send.
Why? Because pros don’t guess. They calculate.
Step Into the War Room: How Real Operators Predict Revenue
Back when I was VP of Retention, I had to forecast email and SMS revenue months in advance.
Let me paint a picture.
You’re sitting in a room with your CEO, the CFO, and a CMO asking you:
“What will our email revenue be next quarter?”
If your answer is, “Well, depends on the sale,” you’re out.
If you can’t speak in numbers, you’re not in the room.
So I built a system.
Now we use it across every single brand we manage.
It’s simple. It’s fast. It works.
I call it Ecommerce Napkin Math.
The Ecommerce Napkin Math Formula
This isn’t fancy AI or some predictive algorithm with 78 filters.
It’s literally:
A segment size
Times open rate
Times click-through rate
Times conversion rate
Times average order value
Let’s break it down:
Email Revenue = Segment Size × Open Rate × Click Rate × Conversion Rate × AOV
That’s it. That’s the formula.
Simple? Yes.
But don’t confuse simplicity with stupidity. Most brands never even think this far.
Let’s go through each component and reverse-engineer how the big brands think.
1. Segment Size
You can’t sell if no one’s listening.
Your segment is the audience that’s going to get the email. NOT your entire list. I’m talking about your product-specific, purchase-intent-driven segment.
This is where 90% of brands screw up.
They send to everyone.
But not everyone wants the thing you’re selling. That’s lazy and dangerous.
You want what I call a Product Affinity Segment — people who are practically waving their wallets in your face.
These are folks who have:
Viewed the product
Added it to cart
Clicked an ad
Started checkout
Bought something similar
Searched for it
Or are algorithmically predicted to want it
Pull that list. Even if it’s only 4,921 people — that’s your segment.
Quality over quantity. Always.
2. Open Rate
This is attention.
How many people are opening your emails?
If your subject lines are garbage, your open rate tanks, and the rest of the math doesn’t matter.
Industry average? 20-30%.
But if your list is warmed up and your subject lines are written by someone who knows how to grab attention, you can get 35-45% easy.
Use historical averages from your ESP (Klaviyo, Postscript, etc). Be conservative.
If you haven’t emailed in weeks and your last open rate was 8%… don’t project 40%.
Be honest with the data. Or the formula lies.
3. Click Rate
This is interest.
What percent of people clicked the link after opening?
Most brands hover between 1–3%.
If your offer sucks, your design confuses people, or your CTA is buried, you’re toast.
If you’re segmenting well and using offer-driven copy, you can push 5–10%.
Again — be real. Don’t use best-case scenarios. Use averages.
4. Conversion Rate
This is decision.
What % of clickers turned into buyers?
This is the biggest variable.
Why?
Because traffic doesn’t equal sales.
You might drive 1,000 clicks and sell 4 items. That’s 0.4%. You might drive 250 clicks and sell 50. That’s 20%.
Depends on:
Product price
Landing page
Offer strength
Trust elements (reviews, badges, etc)
But here’s a rule of thumb:
If the traffic is warm (returning customers), expect 3–5%.
If the traffic is cold (non-buyers), expect 0.5–2%.
5. AOV (Average Order Value)
This is the payout.
What’s your average order size for this specific product?
Don’t use store-wide AOV if this is a niche offer.
If you’re selling a $47 product, and the cart bumps bring it to $62, that’s your number.
Let’s Run the Numbers (Real Example)
Let’s say you want to send an email promoting a $65 product.
You build an affinity segment of:
5,000 subscribers
And your averages look like this:
Open rate = 30%
Click rate = 3%
Conversion rate = 2%
AOV = $65
Here’s how it plays out:
5,000 × 0.30 = 1,500 opens
1,500 × 0.03 = 45 clicks
45 × 0.02 = 0.9 conversions (round up to 1)
1 × $65 = $65
ONE. SALE.
All that work for $65.
Is that worth sending?
Probably not.
Now you see why this math matters.
The Brutal Truth: Sometimes the Numbers Say “DON’T SEND”
And that’s a GOOD thing.
You save your list. You avoid unsubscribes. You preserve trust.
No one unsubscribes because you didn’t send them something.
They unsubscribe when you send them crap.
So instead of asking, “What can I send this week?” — start asking, “Who actually wants this?”
Then run the math.
If the result doesn’t justify the effort, don’t send.
Simple.
Flip the Script: Sell What People Want to Buy
Most ecommerce founders are stuck in this loop:
Come up with an idea.
Blast it to the list.
Hope it sells.
Then they blame “email isn’t working anymore.”
That’s nonsense.
Email is the highest ROI channel you have.
But you’re probably using it wrong.
Instead of pushing products you want to move, start aligning with what your customers already want.
Use your data. Create smart segments. Sell accordingly.
“No one wants to be sold, but everyone loves to buy.”
That’s the game.
Want to Be a Pro? Do This Weekly.
Here’s your simple 3-step assignment this week:
1. Build Your Affinity Segment
Look at your product. Then pull a segment of people who have:
Viewed it
Carted it
Clicked it
Engaged with content around it
Label it. Save it.
2. Run the Formula
Use the formula:Segment × Open Rate × Click Rate × Conversion Rate × AOV
Plug in real data.
If you want my Excel sheet, just email my team.
3. Decide: Send or Don’t Send
If it doesn’t meet your revenue target — skip it.
If it crushes — build the campaign and scale.
This is how you win.
Why This Works (And Why Most Brands Never Do It)
Because most brands are lazy.
They wing it.
They “feel” like sending something.
They don’t look at the math. They don’t track the metrics. They just launch.
Then they complain about poor performance.
That’s amateur hour.
You want to be a pro?
Start running your campaigns like a numbers-driven business, not a creative playground.
Creativity is great. Math pays the bills.
Final Thoughts
The difference between a $100K brand and a $10M brand isn’t their list size.
It’s how they leverage the list.
Napkin Math gives you clarity.
It takes 3 minutes to run. But it tells you EVERYTHING.
Every campaign you launch without running the numbers is just noise.
Run the formula. Send what’s profitable. Kill what’s not.
That’s how you grow.
Need a free email & SMS audit that shows you exactly how to win like this?
Take action now:
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