Unit economics
Model customer lifetime value against acquisition cost, with payback period.
- Category
- Unit economics
- Signup
- None
- Your data
- Stays in your browser
- Also in
- Claude, via MCP
What is a good LTV to CAC ratio?
A good LTV to CAC ratio is 3:1 or higher, meaning a customer returns at least three times what it cost to acquire them. Below 1:1 you lose money on every customer. Well above 5:1 can mean you are underinvesting in growth. Read the ratio together with CAC payback: 12 months or less is a common SaaS bar.
Healthy, at 6.7:1 each acquisition returns well above the 3:1 rule of thumb. Room to spend more if payback (5.0 mo) stays reasonable.
Uses gross-margin LTV (a conservative, CFO-friendly definition). Assumes steady-state churn and margin.
About this calculator
LTV:CAC is the single ratio investors and operators use to judge whether a growth engine actually works, whether it costs you more to acquire a customer than that customer is ever worth. This calculator builds both sides from primary inputs, ARPA, margin and churn on the LTV side, spend and new customers on the CAC side, rather than asking you to already know LTV and CAC as finished numbers.
How to use it
- Under Lifetime value, enter monthly ARPA (average revenue per account), gross margin, and monthly churn rate.
- Under Acquisition cost, enter total sales and marketing spend for the period and the number of new customers that spend acquired.
- Read the LTV:CAC ratio, and check it against the 3:1 rule of thumb shown in the verdict.
- Use CAC payback, months to recover CAC from gross-margin revenue, as a cash-flow check alongside the ratio.
Methodology
Average customer lifetime is 1 ÷ monthly churn rate. At 3% monthly churn, average lifetime is 33.3 months.
LTV here is gross-margin LTV: ARPA × gross margin × average lifetime. Using gross margin rather than raw revenue is the more conservative, CFO-defensible definition, it reflects what a customer is actually worth after cost of delivery, not top-line revenue.
CAC is total sales and marketing spend for the period ÷ new customers acquired in that period. This is a blended CAC across all channels, not per-channel.
CAC payback in months is CAC ÷ (ARPA × gross margin), how many months of gross-margin revenue from one customer it takes to recover what was spent acquiring them.
The 3:1 ratio and payback benchmarks used in the verdict are common SaaS heuristics, not universal laws, capital-efficient businesses often run higher, venture-backed growth-stage companies sometimes run lower deliberately to buy market share.
LTV to CAC ratio formula (as this calculator computes it)
Average lifetime (months) = 1 ÷ Monthly churn LTV = ARPA × Gross margin × Average lifetime CAC = Sales + marketing spend ÷ New customers acquired LTV : CAC = LTV ÷ CAC CAC payback (months) = CAC ÷ (ARPA × Gross margin)
- ARPA
- Monthly revenue per account: recurring revenue for the month ÷ active paying accounts.
- Gross margin
- Share of revenue left after cost of delivery (hosting, support, onboarding, payment fees), entered as a percentage.
- Monthly churn
- Share of customers lost per month, entered as a percentage. 3% gives an average lifetime of 33.3 months.
- Sales + marketing spend
- Everything spent to win new customers in the period: media, salaries, commissions, tools, agencies and events.
- New customers acquired
- Customers won in the same period as the spend.
Because LTV ÷ CAC and CAC payback share the same ARPA × margin term, the two are linked: LTV : CAC = Average lifetime ÷ CAC payback. A 33-month lifetime with a 5-month payback is a 6.7:1 ratio. If churn is entered as zero the lifetime is infinite, so the tool shows a dash instead of a ratio. Very low churn produces very long lifetimes, and many investors cap LTV at three to five years rather than trusting a 100-month figure. The a16z guide to startup metrics goes further and prefers contribution margin over gross margin, and 12- or 24-month LTV when there is little history.
Worked example: an Indian B2B SaaS company
A Bengaluru B2B SaaS company bills an average of ₹25,000 a month per account at an 80% gross margin, with 2.5% monthly logo churn. Last quarter it spent ₹60 lakh on sales and marketing (salaries, LinkedIn and Google Ads, a trade event) and won 30 new customers.
- Average lifetime = 1 ÷ 0.025 = 40 months
- LTV = ₹25,000 × 0.80 × 40 = ₹8,00,000
- CAC = ₹60,00,000 ÷ 30 = ₹2,00,000
- LTV : CAC = ₹8,00,000 ÷ ₹2,00,000 = 4.0 : 1
- CAC payback = ₹2,00,000 ÷ (₹25,000 × 0.80) = ₹2,00,000 ÷ ₹20,000 = 10 months
- Sensitivity: if churn rises to 4%, lifetime falls to 25 months, LTV to ₹5,00,000 and the ratio to 2.5 : 1, while payback stays at 10 months
At 4.0 : 1 with a 10-month payback the company clears both common bars, so adding acquisition spend is defensible if new channels keep CAC near ₹2 lakh. The sensitivity line shows why churn is the input to watch: a 1.5-point rise in monthly churn cuts the ratio by more than a third without any change in marketing efficiency. Payback does not move with churn at all, which is why it is worth reading both numbers.
Commonly cited LTV : CAC and payback guidelines
| Metric | Guideline | Context |
|---|---|---|
| LTV : CAC | Higher than 3, sometimes 7 or 8 | Ratio seen in the best SaaS businesses; described as a guideline, not a rule |
| CAC payback | Under 12 months | Beyond 12 months profitability is described as weak |
| CAC payback (best SaaS) | 5–7 months | Months to recover CAC in many of the best SaaS businesses |
CAC payback benchmarks by business type
| Business type | Healthy CAC payback |
|---|---|
| SaaS | 12 months or less, high performers about 5–7 months |
| B2C | 12 months or less |
| B2B | Can exceed 12 months depending on the business, because sales cycles are longer and CAC higher |
What is a good LTV : CAC ratio?
3:1 is the reference point, and David Skok notes the best SaaS businesses run above 3, sometimes as high as 7 or 8. What counts as good depends on how you built the inputs and where the company is:
- Below 1 : 1: each customer is worth less than it costs to win. Fix churn, pricing or CAC before adding budget.
- 1 : 1 to 3 : 1: profitable per customer but thin, especially once overheads are counted. Common in early channels that have not been optimised yet.
- 3 : 1 to 5 : 1: healthy for most subscription businesses, provided payback is also within your cash runway.
- Above 5 : 1 with short payback: often a sign of underinvestment. You could probably buy faster growth by accepting a higher CAC.
A useful decision rule is to approve extra acquisition spend only when the marginal ratio (the ratio for the extra customers that spend brings) stays above 3 : 1 and payback stays inside 12 months, or inside 18 to 24 months only if you have the cash to fund it. Sales-heavy enterprise motions sit at the long end; self-serve products should be well inside it. For the cash side, use the CAC payback period matrix, and to see how retention changes the ratio, try the LTV growth multiplier simulator.
LTV : CAC in India vs the US
Indian SaaS and D2C teams usually face lower salary costs but also lower ARPA for domestic customers, so the ratio can look similar while absolute CAC is much smaller. Two adjustments matter. First, GST: Google India charges 18% GST on ad invoices, which registered businesses can usually claim as input tax credit (ClearTax), so count spend net of recoverable GST, and use ARPA net of GST too. Second, mixed books: companies selling to both Indian and US customers should run the ratio separately per market, because a blended ARPA hides very different CAC levels. For D2C brands with no subscription, replace monthly churn with a repeat-purchase-based lifetime and treat cash-on-delivery returns as lost revenue before calculating margin. The fully loaded CAC guide covers what belongs in the spend figure.
US SaaS buyers generally pay higher ARPA and the cost of US sales headcount is high, so CAC is driven more by salaries and commissions than by media. Sales tax is not normally part of SaaS revenue reporting, so ARPA is simpler to define. Because sales-led US motions often have longer cycles, match the spend period to when the won customers actually entered the pipeline, or a quarter of heavy hiring will make CAC look worse than it is. Companies selling into the US from India can also use the fractional CMO for B2B SaaS page for how those motions are usually structured.
Common LTV : CAC mistakes
- Using revenue LTV instead of margin LTV. Leaving out cost of delivery inflates the ratio: at a 60% gross margin, revenue LTV is 1.67 times margin LTV.
- Counting only ad spend in CAC. Salaries, commissions, SDR tools and agency retainers are acquisition costs and usually larger than media in B2B.
- Mixing periods: spend from one quarter divided by customers who entered the pipeline two quarters earlier. Match spend to the cohort it produced, or use a rolling 6 to 12 months.
- Trusting a near-zero churn figure from a young company. With six months of history, a 0.5% churn rate implies a 200-month lifetime that no one has observed. Cap lifetime or use 24-month LTV.
- Reporting only a blended ratio. A blended number can hide a paid channel running below 1 : 1 behind strong referral or organic acquisition.
- Ignoring expansion revenue and price rises. This tool uses steady ARPA, so if accounts grow over time, the ratio is conservative; if discounts expire into churn, it is optimistic.
Sources
- SaaS Metrics 2.0 – A Guide to Measuring and Improving what Matters, For Entrepreneurs (David Skok). Accessed 2026-10-17.
- What is the CAC payback period?, Stripe. Accessed 2026-10-17.
- 16 Startup Metrics, Andreessen Horowitz (a16z). Accessed 2026-10-17.
- A Complete Guide to GST and TDS Rate on Promotion Via Google Ads, ClearTax. Accessed 2026-10-17.
FAQ
Revenue LTV overstates what a customer is worth because it ignores cost of delivery, support, hosting, cost of goods. Gross-margin LTV (ARPA × margin × lifetime) is the number a CFO or investor will actually underwrite, since it reflects money that's really available to spend on acquiring the customer in the first place.
It's a widely used SaaS heuristic, not a hard rule. Below 1:1 you're losing money on every customer. Between 1:1 and 3:1 you're profitable but thin. Above 3:1 with fast payback, you likely have room to spend more aggressively on acquisition without hurting unit economics.
This calculator assumes a single blended churn rate, which understates LTV for your best cohorts and overstates it for your worst. If cohorts diverge significantly, run this separately for your strongest and weakest segments rather than relying on one blended number.
No, use total sales and marketing spend, salaries, tools, ad spend, everything that went into acquiring those new customers. A CAC that only counts media spend and ignores sales headcount will look artificially efficient.
A healthy LTV:CAC ratio doesn't rule out leaks elsewhere, lead response time, paid attribution accuracy, and funnel conversion all sit outside this one ratio. The Revenue Systems Health Score chains this question with 11 others across RevOps, paid media, funnel, and strategy to catch what a single ratio can't.
Work out LTV as monthly ARPA × gross margin ÷ monthly churn, work out CAC as sales and marketing spend ÷ new customers in the same period, then divide LTV by CAC. A result of 4 means each customer is expected to return four times their acquisition cost in gross margin.
Yes. A ratio far above 5 : 1 with fast payback usually means the company could spend more on acquisition and still grow profitably. It can also mean the inputs are flattering the result, for example a churn rate measured over too short a period or a CAC that leaves out sales salaries.
LTV : CAC measures total return over the customer lifetime, while CAC payback measures how quickly you get the acquisition cost back in cash. A company can have a strong ratio and still run short of money if payback takes two years, so investors look at both.
There is no monthly subscription churn, so build LTV from average order value × gross margin × expected orders per customer over a fixed window, often 12 or 24 months. Use contribution margin after shipping, returns and payment fees, and for India deduct RTO losses on COD orders before you compare it with CAC.
Monthly on a rolling basis is common for operating decisions, with a quarterly view for board reporting. Recalculate whenever pricing, a major channel or the sales team changes, because each of those shifts one side of the ratio quickly.
Numbers looking off?
If the model says one thing and the pipeline says another, that gap is usually where the revenue is. A 30-minute call finds it.
It starts with a 30-minute call. Pick a time below.