Customer Acquisition Cost (CAC) Calculator (VND)
Customer acquisition cost (CAC) is the average amount you spend to win one new customer. The base calculation is deliberately simple: take all your sales and marketing spend over a period and divide it by the number of new customers it produced. If you run a business in Vietnam and budget in dong, this is the number that tells you whether growth is actually affordable. Spend 600.000.000 VND on ads, sales salaries and promotions in a quarter and acquire 150 customers, and your CAC is 600.000.000 ÷ 150 = 4.000.000 VND per customer.
CAC means little on its own — whether 4.000.000 VND is cheap or expensive depends entirely on how much a customer is worth over their lifetime (LTV). The gross-margin version of LTV is average monthly revenue × gross margin × the number of months a customer stays. With a customer paying 2.500.000 VND a month at a 45% gross margin for 18 months, LTV = 20.250.000 VND. Set against a CAC of 4.000.000 VND, the LTV:CAC ratio is 5.1 — every dong spent on acquisition returns roughly 5.1 dong of lifetime gross profit.
The calculator above lets you enter marketing spend, new customers, average revenue per customer, gross margin and customer lifespan, then instantly returns CAC, LTV, the LTV:CAC ratio and the CAC payback period — the number of months of gross profit it takes to earn the acquisition cost back (about 3.6 months in this case). One caveat throughout: the margins, lifespans and spend levels in these examples are illustrative inputs, not industry benchmarks. Replace them with your own real figures before drawing conclusions.
How the calculator works out CAC and LTV:CAC
The four core formulas
| Metric | Formula |
|---|---|
| CAC | Total sales & marketing spend ÷ New customers |
| LTV | Monthly revenue × gross margin × lifespan in months |
| LTV:CAC | LTV ÷ CAC |
| CAC payback (months) | CAC ÷ (Monthly revenue × gross margin) |
Plugging in the EN example: CAC = 600.000.000 ÷ 150 = 4.000.000 VND. LTV = 2.500.000 × 45% × 18 = 20.250.000 VND. LTV:CAC = 20.250.000 ÷ 4.000.000 = 5.1. Monthly gross profit per customer = 2.500.000 × 45% = 1.125.000 VND, so CAC payback = 4.000.000 ÷ 1.125.000 ≈ 3.6 months.
Why LTV uses gross margin, not revenue
A common mistake is to compute LTV from revenue and conclude the unit economics look great. But payroll, infrastructure and cost of goods all sit between revenue and profit. The calculator multiplies by gross margin so LTV reflects the real profit a customer leaves behind, which is the only fair thing to compare against CAC. Two companies with identical revenue but different margins will have very different LTV:CAC ratios.
How to read the ratio
- LTV:CAC below 1 means you lose money on every customer — each sale makes the hole deeper.
- LTV:CAC around 3 is the rule-of-thumb target often cited in the startup world as "healthy".
- A very high ratio (like the one in the worked example) can be a signal you are underinvesting in growth — sometimes the right move is to accept a higher CAC and expand faster, as long as the payback period stays acceptable.
What the model leaves out
The tool assumes a constant gross margin and lifespan, ignores retention/expansion spend, does not separate marketing channels, and omits the time value of money. In practice CAC varies sharply by channel, customer lifespan is hard to estimate for a young company, and some spend (brand) pays off with a lag. Treat the output as a high-level read on your unit economics, not an exact accounting figure.
Worked example: 600.000.000 VND of spend, 150 new customers
Illustrative assumptions: each customer pays 2.500.000 VND a month at a 45% gross margin and stays 18 months. These are inputs for illustration, not benchmarks.
| Metric | Calculation | Result |
|---|---|---|
| CAC | 600.000.000 ÷ 150 | 4.000.000 VND |
| LTV (gross profit) | 2.500.000 × 45% × 18 | 20.250.000 VND |
| LTV : CAC | 20.250.000 ÷ 4.000.000 | 5.1 |
| CAC payback | 4.000.000 ÷ 1.125.000 | 3.6 months |
Three things stand out.
- The economics clear the healthy bar. An LTV:CAC of 5.1 sits above the rule-of-thumb 3, meaning each acquisition dong returns well over a dong of lifetime gross profit. That is the green light to keep the channel running.
- Payback drives cash flow. With 1.125.000 VND of gross profit per customer each month against a 4.000.000 VND CAC, you recover the cost in about 3.6 months. A shorter payback means cash recycles faster and you can fund more growth from the same budget.
- Pressure-test the inputs. Gross margin and lifespan move LTV the most, and they are the hardest to estimate honestly. Re-run the tool with a shorter lifespan or thinner margin to see how quickly a comfortable ratio erodes.
Enter your own numbers and revisit them every quarter rather than calculating once and forgetting. FiMo also has customer lifetime value (CLV) and break-even calculators if you want to dig deeper into the same unit economics.
Frequently asked questions
What is CAC and how do you calculate it?
Customer acquisition cost (CAC) is the average cost to win one new customer: total sales & marketing spend divided by the number of new customers in the same period. Illustrative example: spend 600.000.000 VND and acquire 150 customers and CAC = 600.000.000 ÷ 150 = 4.000.000 VND per customer. Include ad budget, sales and marketing salaries, tooling and acquisition promotions so the figure reflects reality.
What is a good LTV:CAC ratio?
An LTV:CAC of about 3 is the widely cited rule of thumb for healthy unit economics: every acquisition dong returns roughly three dong of lifetime gross profit. Below 1 means you lose money per customer. A very high ratio (like the 17.3 in this page's main example) is not automatically ideal — it can signal you are underinvesting in growth. Treat 3 as a reference point, not a hard rule; expectations differ by industry and stage.
How is LTV calculated here?
This tool uses gross-margin LTV = average monthly revenue × gross margin × the number of months a customer stays. Example: 2.500.000 VND/month × 45% × 18 months = 20.250.000 VND. Multiplying by gross margin (rather than using revenue alone) makes LTV reflect the real profit a customer leaves behind, which is what you should compare against CAC.
What is CAC payback period?
CAC payback is the number of months of gross profit it takes to recover the cost of acquiring a customer: CAC ÷ (monthly revenue × gross margin). Example: 4.000.000 ÷ 1.125.000 ≈ 3.6 months. A shorter payback is better — you get your money back before the customer can churn, so cash recycles faster and acquisition is less risky.
Which costs should be included in CAC?
Include all direct costs that generate new customers: ad spend (Facebook, Google, TikTok), sales and marketing salaries and commissions, tooling (CRM, landing pages), content, events and acquisition promotions. Keep retention spend on existing customers separate, since that is not an acquisition cost. Leaving costs out makes CAC look artificially low and your unit economics look better than they really are.
How do I fix a CAC that is too high?
You have two levers: lower CAC or raise LTV. Cut CAC by optimising ad channels, improving landing-page conversion, focusing on segments that close easily, and leaning on referrals (close to free). Raise LTV by improving gross margin, upselling and cross-selling, and increasing retention. If CAC tripled to 7.500.000 VND while LTV held, the LTV:CAC ratio in the main example would fall to 5.8 — still workable, but worth watching closely.