Investor Q&A Drills: Six Rapid CAC/LTV/ROAS/Payback Reps
Objective: Build calculation speed and formula recall for CAC, LTV, ROAS, and payback across six short, varied scenarios pulled from a real campaign export, the way an investor or CFO fires off follow-up numbers in a live meeting with no time to look up the formula.
You're prepping for a fundraising Q&A in the hustle spirit of Zomato's early growth years (35x oversubscribed IPO, built on unit-economics discipline it had to earn before anyone gave it credit). Investors don't ask one clean question, they fire six half-finished ones back to back, and you need the formula cold.
This is a drill project, not a single deep dive: six short numeric reps, each pulling real numbers from the same campaign export used elsewhere in this track. Work through them in order, then check your math against the worked answer.
Before you start
What you'll need
Free path (everything below is enough to finish)
Not in the tools directory, genuinely free, all six drills are single-formula calculations.
The process
6 steps
Step 01 of 06
CAC = Total Spend / New Customers Acquired.
The "Core Terms" search ad group spent $340.08 and produced 3 new customers over its first 9 days. What's the CAC?
Procedure
- Sum the cost column for the filtered rows: $340.08.
- Sum the conversions column for the same rows: 3.
- Divide: $340.08 / 3.
CAC = $340.08 / 3 = $113.36 per customer
Healthy
Under the relevant sector benchmark (SaaS: $205, Retail: $87).
Unhealthy
Well above sector benchmark with no offsetting LTV story.
What this means
$113.36 sits comfortably under the $205 SaaS benchmark but above the $87 Retail benchmark, the verdict depends entirely on which sector this company is in.
So what do I do about it?
| Symptom | Action | Effort |
|---|---|---|
| a CAC number is stated with no sector benchmark next to it | always state the benchmark next to the number, a number with no comparison persuades nobody | 5 min |
Step 02 of 06
CAC = Total Spend / New Customers Acquired.
"Competitor Terms" spent $82.91 and produced 3 conversions over the same 9-day window. What's the CAC, and how does it compare to Core Terms?
Procedure
- Sum the cost column: $82.91.
- Sum the conversions column: 3.
- Divide: $82.91 / 3.
- Compare against Core Terms' $113.36 from Drill 1.
CAC = $82.91 / 3 = $27.64 per customer, less than a quarter of Core Terms' $113.36
Healthy
Meaningfully lower CAC than the account's other ad groups, worth investigating why.
Unhealthy
N/A here, this is the efficient outlier in this pair.
What this means
Competitor Terms is roughly 4x cheaper per customer than Core Terms despite similar conversion volume, that's a budget-reallocation conversation, not a footnote.
So what do I do about it?
| Symptom | Action | Effort |
|---|---|---|
| a cheaper ad group is getting the same budget share as an expensive one | flag for reallocation in the next budget review | 30 min |
Step 03 of 06
LTV = (Monthly Revenue per Customer x Gross Margin %) / Monthly Churn Rate.
A customer pays $80/month, gross margin is 70%, and monthly churn is 4%. What's their LTV?
Procedure
- Monthly gross profit: $80 x 0.70 = $56.
- Divide by churn: $56 / 0.04.
LTV = ($80 x 0.70) / 0.04 = $56 / 0.04 = $1,400.00
Healthy
Healthy if CAC for this customer is under roughly $466 (a 3:1 ratio).
Unhealthy
Someone plugs $80 revenue straight into the ratio instead of $56 gross profit.
What this means
$1,400 is the correct LTV only because gross profit ($56), not revenue ($80), was divided by churn.
So what do I do about it?
| Symptom | Action | Effort |
|---|---|---|
| team plugs $80 revenue straight into a ratio instead of $56 gross profit | flag it before it reaches a fundraising deck | 5 min |
Step 04 of 06
Always use gross profit, not revenue, and always re-derive a ratio before repeating it.
Someone on the team calculates LTV as $80 x 0.70 x 25 months = $1,400 and separately claims an 8:1 LTV:CAC against a $175 CAC. Spot the error, then recalculate.
Procedure
- Check whether the $1,400 already includes gross margin: $80 x 0.70 x 25 = $1,400 is correct math for a 25-month average lifetime.
- Recompute the ratio: $1,400 / $175.
- Decide whether the claimed ratio is actually correct or not.
$1,400 / $175 = 8:1 exactly. The claim was correct this time, the trap is realizing you have to check the math instead of assuming a stated ratio is right or wrong.
Healthy
8:1 is real and comfortably above the 3:1 floor.
Unhealthy
N/A, this drill exists to build the habit of checking, not to catch a planted error every time.
What this means
Fast mental math confirms $80 x 0.70 = $56 and $56 x 25 = $1,400, always verify a stated ratio before repeating it in your own deck.
So what do I do about it?
| Symptom | Action | Effort |
|---|---|---|
| a stated ratio gets forwarded without anyone re-deriving it | re-derive every LTV:CAC ratio you're handed before you cite it externally | 5 min |
Step 05 of 06
ROAS = Revenue Generated by Ads / Ad Spend.
The "Social - Prospecting Lookalike" ad group spent $142.78 over 2026-06-10 through 2026-06-14 and drove 29 conversions worth $22 each in first-purchase revenue. What's the ROAS?
Procedure
- Revenue: 29 x $22 = $638.
- Divide by spend: $638 / $142.78.
ROAS = $638 / $142.78 = 4.47x
Healthy
Above the e-commerce 4:1 typical target the lesson cites.
Unhealthy
Below the 2.04 e-commerce median.
What this means
4.47x clears even the ambitious 4:1 e-commerce target, but remember the lesson's warning: platforms overstate ROAS by 2.3x on average, verify against your own revenue records before reporting this number externally.
So what do I do about it?
| Symptom | Action | Effort |
|---|---|---|
| a 4.47x ROAS gets reported straight from the ad platform | cross-check against actual bank or payment-processor revenue before it goes in a deck | 30 min |
Step 06 of 06
Payback Period (months) = CAC / Monthly Gross Profit per Customer.
CAC is $220, monthly gross profit per customer is $19. What's the payback period, and is it healthy?
Procedure
- Divide: $220 / $19.
- Compare against the under-18-month floor and the ~20-month 2025 SaaS median.
Payback = $220 / $19 = 11.58 months
Healthy
Under 12 months, the lesson's stated ideal, and well under the ~20-month 2025 median.
Unhealthy
N/A here.
What this means
11.58 months clears even the strict under-12-month ideal, not just the looser 18-month floor, a green light on cost alone.
So what do I do about it?
| Symptom | Action | Effort |
|---|---|---|
| payback looks fine in isolation | still check LTV:CAC before recommending a budget increase, a fast payback with a thin LTV:CAC can still be a mediocre channel | 5 min |
Final deliverable
Six worked answers, one per drill, each showing the formula, the plug-in, and the final number.
See a reference example
Drill 1: $113.36. Drill 2: $27.64 (4x cheaper than Drill 1). Drill 3: $1,400.00. Drill 4: 8:1, ratio checks out. Drill 5: 4.47x. Drill 6: 11.58 months. A team prepping the same drills for a company at Swiggy's scale would run this exact six-question set before every board deck, the numbers change, the formulas never do.
Success criteria
You're done when you can:
- All 6 answers match the worked math within rounding
- Drill 1 vs. Drill 2 comparison correctly flags Competitor Terms as the more efficient channel
- Drill 3 uses gross profit, not raw revenue, in the LTV formula
- Drill 6 correctly clears both the 12-month ideal and the 18-month floor