From the event · How to Scale Ad Spend
Find your scaling target.
Most brands scale to the wrong CAC. They chase a blended average and quietly acquire customers at a lifetime loss. This runs the exact math Abir walked through, so you can find the spend level that hits peak cohort profit, not more, not less.
Based on the Profit Last framework by Abir Syed, CPA. Plug in your numbers below.
Back-of-napkin CAC math has three flaws
The usual "price minus costs equals my CAC target" hides three problems. This calculator is built to beat all three.
Your margins are probably wrong
Freight, duties, tariffs, broker fees and un-trued-up estimates get missed. If your margin is off, every target is off. Use your true gross margin below.
LTV is a fuzzy number
Retention shifts, you sell on other channels, and last year's LTV isn't this year's. Watch your subscription mix as a leading signal, and refresh often.
There isn't one CAC. There are two.
Your blended average CAC is what you see. Your marginal CAC, the cost of the next customer, is what actually decides profit. This is the big one.
Your scaling target
Everything updates live. Numbers are pre-filled with Abir's example so you can see it working, then swap in your own.
Step 1 · Your true unit economics
Step 2 · Calibrate your CAC curve
Two real spend scenarios you can estimate. As you push spend, you acquire more customers but blended CAC rises. This is the calibration exercise Abir describes.
Step 3 · Where are you now? (optional)
Your scaling-target CAC
$47
The blended CAC to actually aim for. Above this, you start losing money on the margin.
Marginal CAC ceiling
$70
Most you can pay for the next customer.
Target customers / cohort
370
Where cohort profit peaks.
Target spend / cohort
$17,344
Total acquisition spend at the peak.
Peak cohort profit
$8,556
The most profit this cohort can make.
Cohort profit as you scale
Profit climbs, then peaks where marginal CAC meets your gross-profit ceiling. Past the peak it falls away, and the whole game is pushing this peak further to the right.
Average vs marginal CAC at each spend level
Average CAC is what your systems show. Marginal CAC is the cost of the next customer. Once marginal CAC crosses your $70 ceiling, every additional customer is a lifetime loss.
| Customers / cohort | Marginal CAC | Average CAC | Cohort profit |
|---|---|---|---|
| 90 | $35 | $29 | $3,656 |
| 190 | $48 | $36 | $6,531 |
| 280 | $59 | $41 | $8,050 |
| 370 | $70 | $47 | $8,556 |
| 460 | $81 | $53 | $8,050 |
| 560 | $94 | $59 | $6,300 |
| 740 | $116 | $70 | $0 |
Your scaling target moves. Runneth can watch it for you.
Margins drift, LTV shifts, and CAC creeps every week, so the peak you found today won't be the peak next month. Runneth can build you a routine that monitors CAC and cohort profit in real time and pings you the moment you drift into the lifetime-loss zone, so you never miss the signal again.