01
Enter LTV inputs
ARPA (monthly revenue per customer), gross margin %, and monthly churn rate — these three determine LTV.
Startup Unit Economics Calculator
LTV, CAC, LTV:CAC ratio, and CAC payback — with the 3× benchmark.
Updated Reviewed by Sajid Hussain· Editor
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Last updated
June 2, 2026
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9 markets · 8 currencies
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The metrics every investor asks about
LTV, CAC, LTV:CAC ratio, and payback — computed correctly
A unit economics calculator answers the question every Series A investor will ask: does your business make more money from a customer than it costs to acquire them — and by how much? This tool computes LTV, CAC, the LTV:CAC ratio with the 3× benchmark, and the CAC payback period — the four metrics that determine whether your growth is profitable or a money-burning exercise.
**LTV must use gross margin, not revenue.** The correct formula is LTV = (ARPA × Gross Margin %) ÷ Monthly Churn Rate. A product with $200 ARPA, 75% gross margin, and 2% monthly churn has an LTV of $7,500 — not $10,000. Using raw revenue inflates LTV and makes the ratio look better than it is. Every serious investor checks whether you're using gross-profit LTV; using revenue LTV is an immediate red flag.
**The 3× LTV:CAC benchmark is a floor, not a goal.** The a16z "rough benchmark for consumer companies" is ≥ 3× — meaning LTV should be at least 3 times your CAC. Below 1× you are literally losing money on every customer you acquire. Between 1× and 3× your unit economics are questionable. Above 3× the model is investor-grade. Above 5× you either have exceptional economics or you're underinvesting in growth.
**CAC payback is the cash-flow indicator.** A strong LTV:CAC ratio does not mean you have great cash flow — it means the economics are good in steady state. CAC payback (CAC ÷ gross margin per month) is what stresses cash: a 24-month payback means each customer spends two years in "debt" before contributing net cash. Under 12 months is strong; over 18 months requires either high retention (long LTV justifies the wait) or a capital raise to fund growth.
**Churn is the fastest LTV lever.** Because LTV = gross margin / churn, halving the churn rate always doubles LTV regardless of ARPA or margin. This tool shows the LTV sensitivity to churn changes directly — the "LTV at half churn" output quantifies exactly what a retention improvement is worth. Reducing churn from 4% to 2% monthly doubles LTV, cuts CAC payback in half, and typically raises the LTV:CAC ratio above every threshold in one move.
Quick facts
- LTV formula
- (ARPA × GM%) ÷ Churn — gross-profit-based
- LTV:CAC benchmark
- 3× investor floor — surfaced with context
- Payback period
- CAC ÷ gross margin/month — cash-flow view
- Churn sensitivity
- LTV at half churn — shows retention value
- CAC formula
- (Sales + Marketing) ÷ New Customers
- Any currency
- Global — works for USD, GBP, INR, EUR, AUD
How it works
From three inputs to a full investor-ready picture
Three LTV inputs, three CAC inputs — under a minute.
02
Enter CAC inputs
Monthly sales spend, monthly marketing spend, and new customers acquired — these three determine CAC.
03
Read the ratio
LTV:CAC ratio appears instantly with a benchmark verdict. See whether your economics are unprofitable, weak, adequate, or investor-grade.
04
Check payback and sensitivity
CAC payback shows the cash-flow picture; LTV at half churn shows what a retention improvement is worth.
Steps to use the Unit Economics Calculator: Enter LTV inputs, Enter CAC inputs, Read the ratio, Check payback and sensitivity.
Formula
The unit economics formulas — sourced from a16z and Wall Street Prep
These are the investor-standard formulas, not simplified approximations.
01
Customer Lifetime Value (LTV)
LTV = (ARPA × Gross Margin %) ÷ Monthly Churn Rate
ARPA = average revenue per account per month; GM = gross margin as a decimal; Churn = monthly churn rate as a decimal. Using gross margin (not revenue) is essential — it measures what the customer is actually worth to the business.
Example: $200 × 0.75 ÷ 0.02 = $7,500 LTV at 75% GM and 2% monthly churn.
02
Customer Acquisition Cost (CAC)
CAC = (Sales Spend + Marketing Spend) ÷ New Customers Acquired
Include all sales and marketing costs for the same period as the new customer count. Common errors: using only paid-ad spend (underestimates CAC) or including customer-success costs (overstates it).
Example: ($20,000 + $10,000) ÷ 50 customers = $600 CAC.
03
LTV:CAC Ratio
LTV:CAC = LTV ÷ CAC
The core investor ratio. 3× is the widely cited benchmark (a16z "rough benchmark for consumer companies"). Note: B2B SaaS with long-contract customers often runs at higher ratios than 3× due to lower churn.
Example: $7,500 LTV ÷ $600 CAC = 12.5× — well above the 3× floor.
04
CAC Payback Period
CAC Payback (months) = CAC ÷ (ARPA × Gross Margin %)
The number of months until gross margin from the customer recovers the acquisition cost. This is the cash-flow metric — a high LTV:CAC with long payback still strains cash.
Example: $600 CAC ÷ $150 gross margin/month = 4.0 months payback.
Worked example
SaaS startup: $200 ARPA, 75% GM, 2% monthly churn
The same numbers used to build this page — cross-check any SaaS tool against these.
Scenario
A SaaS startup has $200 ARPA, 75% gross margin, 2% monthly churn, spends $30,000/month on sales and marketing, and adds 50 new customers each month. What are its unit economics?
1
Step 1 · Compute LTV
Gross margin per month = $200 × 75% = $150. LTV = $150 ÷ 0.02 = $7,500. Average customer lifetime = 1 ÷ 0.02 = 50 months (~4.2 years).
LTV: $7,500 · Avg lifetime: 50 months
2
Step 2 · Compute CAC
Total acquisition spend = $20,000 sales + $10,000 marketing = $30,000. New customers = 50. CAC = $30,000 ÷ 50 = $600.
CAC: $600
3
Step 3 · LTV:CAC ratio
$7,500 LTV ÷ $600 CAC = 12.5× — well above the 3× investor benchmark. This business makes $12.50 in lifetime gross profit for every $1 spent acquiring a customer.
LTV:CAC: 12.5×
4
Step 4 · CAC payback
$600 CAC ÷ $150 gross margin/month = 4.0 months. Each customer pays back their acquisition cost in just 4 months, then contributes $150/month in gross margin for the rest of their lifetime.
Payback: 4.0 months
The takeaway
Strong unit economics — 12.5× LTV:CAC and 4-month payback. The biggest risk is churn: if monthly churn doubles to 4%, LTV halves to $3,750 and the ratio drops to 6.25×. Retention is the moat.
Unit economics benchmarks
What LTV:CAC and payback to aim for
Widely used by investors and founders. Note: the 3× benchmark was originally cited as a consumer benchmark by a16z; B2B SaaS at low churn often runs higher.
| Metric | Poor | Average | Good | Excellent |
|---|---|---|---|---|
| LTV:CAC ratio | < 1× (losing money) | 1–2× | 2–3× | ≥ 3× (investor benchmark) |
| CAC payback period | > 24 months | 18–24 months | 12–18 months | < 12 months |
| Monthly churn rate | > 5% | 3–5% | 1–3% | < 1% (strong retention) |
| Gross margin (SaaS) | < 50% | 50–65% | 65–80% | > 80% |
Why this calculator
Calcrux vs other LTV CAC calculators
Most free tools calculate either LTV or CAC in isolation and miss the ratio entirely. This one gives the full picture with benchmark context.
| Feature | Calcrux | Typical free tool | Spreadsheet |
|---|---|---|---|
| Gross-margin-based LTV (not revenue) | Manual | ||
| LTV:CAC ratio with 3× benchmark | Manual | ||
| CAC payback period | Manual | ||
| Churn sensitivity (LTV at half churn) | Manual | ||
| Avg customer lifetime in months | Rare | Manual | |
| Investor-grade formula source cited | |||
| Any currency | Usually USD |
Common mistakes
How unit economics calculations mislead
Using revenue instead of gross margin in LTV
Why it matters
LTV based on revenue overstates the true value per customer. A product with 30% gross margin has an LTV 3× lower than revenue-based LTV suggests — and the LTV:CAC ratio looks 3× better than reality.
Fix
Always use (ARPA × gross margin %) ÷ churn for LTV. Enter your gross margin % in the field above.
Treating a > 1 ratio as "fine"
Why it matters
LTV:CAC > 1 means each customer eventually turns a profit, but it says nothing about how long that takes or whether you can fund the growth. A 1.5× ratio with 30-month payback is effectively unprofitable at scale.
Fix
Check the CAC payback period alongside the ratio. Both need to be healthy — ratio shows total economics, payback shows cash flow.
Using blended CAC instead of new-customer CAC
Why it matters
Blending total sales + marketing spend across new and existing customers underestimates the true cost of acquiring a new logo.
Fix
Separate new-customer acquisition spend from retention and expansion spend. Enter only acquisition spend (outbound, ads, SDRs) and new customers.
Ignoring churn as the biggest LTV lever
Why it matters
Most founders focus on growing ARPA to increase LTV. But cutting churn from 4% to 2% doubles LTV with no change to ARPA or margins.
Fix
Check the "LTV at half churn" output to quantify what a retention improvement is worth before investing in a price increase.
Treating 3× as the target rather than the floor
Why it matters
The 3× benchmark is a consumer-company rough guide from a16z. B2B SaaS businesses with low churn and long contracts routinely run at 5–10×. Treating 3× as the goal undersets ambition and can mask weak unit economics in high-churn segments.
Fix
Use 3× as the warning signal for investor conversations, not the ceiling. For B2B SaaS with < 1% monthly churn, benchmark against 5× or higher.
Tips
Build investor-grade unit economics
Hit 3× before scaling spend
Raising the LTV:CAC ratio above 3× before increasing the acquisition budget ensures each new dollar of spend is profitable. Below 3×, more spend means more losses.
Halving churn doubles LTV
Because LTV = GM ÷ churn, cutting churn in half always doubles LTV — more powerfully than raising price or improving margins for most startups.
Track payback too
A strong LTV:CAC with a 30-month payback means you need a lot of capital to fund growth. Target payback under 12 months to fund growth from revenue.
Segment CAC by channel
Blended CAC hides the fact that some channels (e.g. inbound organic) have 0 CAC while others (paid outbound) are expensive. Segment to find where to invest.
Use gross margin, always
Every investor will check whether you used gross-margin LTV or revenue LTV. Being the founder who gets this right instantly builds credibility.
Right-size marketing to CAC payback
If CAC payback is 18 months, you need 18 months of working capital per customer acquired. Size the marketing budget to what you can actually float.
Use cases
When founders reach for this calculator
The Unit Economics Calculator works across every stage of the workflow.
Preparing for a Series A pitch
Compute the investor-grade LTV:CAC ratio and payback period before the first investor meeting to be ready for the inevitable question.
Evaluating a marketing channel
Compare LTV:CAC across acquisition channels to find which channels deserve more budget and which are burning cash.
Deciding whether to raise prices
Raise ARPA by 20% and see how LTV, LTV:CAC, and payback change — quantify the pricing lever before implementing it.
Justifying a retention investment
Use the LTV at half churn output to show the board the dollar value of cutting churn — turning a "nice to have" into a financial imperative.
Stress-testing expansion assumptions
Model a growth plan: if we hire 5 more SDRs (raising sales spend), how many new customers must they generate to keep LTV:CAC above 3×?
Comparing against competitors
If a competitor reports a 3× LTV:CAC, check whether they're using gross-margin LTV or revenue LTV — the difference can flip the comparison entirely.
Glossary
Unit economics vocabulary
Every important term you'll encounter in this calculator and the broader topic.
- ARPA
- Average Revenue Per Account — monthly revenue divided by active paying accounts. The revenue side of LTV.
- LTV (Lifetime Value)
- The total gross profit a customer generates over their lifetime: (ARPA × gross margin %) ÷ monthly churn rate.
- CAC (Customer Acquisition Cost)
- The average cost to win a new paying customer: (sales + marketing spend) ÷ new customers acquired in the same period.
- LTV:CAC ratio
- LTV divided by CAC. The investor benchmark is ≥ 3× — meaning the customer is worth at least 3 times what it costs to acquire them.
- CAC payback period
- Months until gross margin from a customer recovers the acquisition cost: CAC ÷ (ARPA × gross margin %). The cash-flow efficiency metric.
- Monthly churn rate
- The percentage of customers who cancel each month. 2% monthly churn ≈ 21% annually. Because it is in the denominator of LTV, it is the most powerful lever to improve.
- Gross margin
- Revenue minus direct cost of goods sold (COGS), as a percentage. For SaaS, COGS includes hosting, support, and payment processing — not sales or marketing.
Help & answers
Frequently asked questions
Everything you need to know about how the Unit Economics Calculator works.
01How do you calculate LTV:CAC ratio for a startup?
LTV:CAC = LTV ÷ CAC, where LTV = (ARPA × gross margin %) ÷ monthly churn rate and CAC = (sales + marketing spend) ÷ new customers. Using gross margin in LTV is essential — revenue-based LTV overstates the ratio.
02What is a good LTV:CAC ratio for a startup?
3× is the widely cited investor benchmark: LTV should be at least 3 times CAC. Below 1× you lose money per customer. Above 3× your unit economics are investor-grade. B2B SaaS with low churn often runs at 5–10× or higher.
03What is CAC payback period and why does it matter?
CAC payback = CAC ÷ (ARPA × gross margin %). It is how many months until a customer pays back their acquisition cost. Under 12 months is strong; over 24 months strains cash because you need capital to fund growth.
04Should LTV use revenue or gross margin?
Gross margin. LTV = (ARPA × GM%) ÷ monthly churn. A 30% margin product has 3× lower LTV than revenue-based LTV suggests. Investors always check which formula you use — gross-margin LTV is the correct one.
05What is the fastest way to improve LTV?
Reduce churn. Because LTV = GM ÷ churn, halving churn always doubles LTV regardless of ARPA or margins. Cutting churn from 4% to 2% monthly doubles LTV, cuts payback in half, and raises the LTV:CAC ratio above every benchmark.
06How do you calculate customer acquisition cost (CAC)?
CAC = (monthly sales spend + monthly marketing spend) ÷ new customers acquired in the same period. Include all acquisition costs — salaries, commissions, ad spend, tools. Exclude retention and customer-success spend.
07Does this calculator work for any business model?
Best for subscription businesses (SaaS, memberships). For transactional businesses, use ARPA = average order value × monthly purchase frequency and churn rate = 1 − repeat purchase rate.
08Does this unit economics calculator work in any currency?
Yes — fully global. Enter in USD, INR, GBP, EUR, AUD or any other currency and all results come back in it. The formulas are universal.
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Category
Startup & Business Intelligence
Subcategory
strategic planning
Availability
Global · 9 markets
Price
Free forever
Topics
unit economics calculatorLTV CAC calculatorstartup unit economicscustomer lifetime value calculatorcustomer acquisition cost calculatorLTV:CAC ratioCAC payback periodSaaS unit economicsstartup metrics calculatorinvestor metrics calculator
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