The question that keeps founders awake
You spend $500 acquiring a customer. She'll generate $1,500 in total revenue over her lifetime. That's a 3:1 ratio-healthy, right? But what if half your customers churn in month two? Then you never break even on half your acquisition spend. This calculator tears back the curtain on the brutal truth: whether your unit economics work or whether you're bleeding money trying to grow.
What This Calculator Does
This tool compares Customer Acquisition Cost (CAC) directly against Customer Lifetime Value (LTV) and shows you the payback period-how many months until a customer's revenue covers what you spent acquiring them. Feed in your total sales and marketing spend, the number of new customers acquired, average revenue per user, and monthly churn rate. The calculator spits out CAC, LTV, the ratio between them, and how long the math takes to work in your favor.
How to Use This Calculator
Step 1: Tally up all your sales and marketing costs. This includes your salary if you're doing sales yourself, hired salespeople, ad spend, marketing automation tools, agencies, commissions, and customer success onboarding for new customers. Be comprehensive. If you spent $50,000 on customer acquisition last quarter, enter 50000.
Step 2: Count how many new customers you actually acquired in that same period. If your ads and sales effort brought in 100 new customers last quarter, enter 100.
Step 3: Calculate your Average Revenue Per User (ARPU). Sum all revenue generated from those new customers in their first month, then divide by the number of new customers. If 100 customers generated $25,000 in their first month, your ARPU is $250.
Step 4: Enter your monthly churn rate as a percentage. If you lost 3 customers out of 100 last month, that's 3%. This rate determines how long the customer relationship lasts and how much total revenue they'll contribute.
Step 5: Hit calculate. The tool shows your CAC, your LTV, the LTV:CAC ratio (the magic number), and payback period (months until revenue covers acquisition cost). A ratio under 2:1 means you're acquiring unprofitably. Over 5:1 and you're underinvesting in growth.
The Formula Behind the Math
Customer Acquisition Cost (CAC)
CAC = Total Sales & Marketing Spend / Number of New Customers Acquired
Example: $50,000 spend / 100 new customers = $500 CAC per customer.
Customer Lifetime Value (LTV)
LTV = (ARPU / Monthly Churn Rate) × Gross Margin
If gross margin is 80%, ARPU is $250, and monthly churn is 3%:
LTV = ($250 / 0.03) × 0.80 = $8,333 × 0.80 = $6,667
LTV:CAC Ratio
Ratio = LTV / CAC
Example: $6,667 / $500 = 13.3:1 ratio (excellent).
CAC Payback Period (months)
Payback = CAC / (ARPU × Gross Margin)
Example: $500 / ($250 × 0.80) = $500 / $200 = 2.5 months to break even.
What this means: you spend $500 acquiring a customer, and in 2.5 months their revenue covers that cost. Everything beyond 2.5 months is profit. Our calculator does all of this instantly-but now you understand exactly what it's computing.
B2B SaaS Companies Evaluating Sales Efficiency
Your enterprise sales team just closed five $500K ARR contracts. The total quota-carrying headcount cost $1M. Your initial reaction: that's a 2.5M CAC for five customers. But LTV on a $500K ARR contract paying for five years is $2.5M (minus churn and cost of goods sold). The ratio is close to even, so you need those deals to stick around. This calculator shows you whether enterprise sales pencils out-and whether you can afford to hire another quota-carrying rep.
Digital Product Creators Testing Customer Worth
You run paid ads and spend $2,000/month to acquire customers at $50 each (40 new customers). Your product generates $80/month ARPU with 5% monthly churn. CAC is $50. LTV is $1,280. Your ratio is 25:1. This tells you to turn up the ad spend; you're massively underinvesting in growth. Your payback is less than one month, so every dollar spent acquiring is paid back and then some.
Founders Deciding Between Acquisition Channels
You have two ways to acquire customers: content marketing (organic, slow, low CAC of $80) and paid ads (fast, higher CAC of $300). If your LTV is $1,200, both channels are profitable (both have ratios above 3:1). But organic has a 15-month payback while paid has a 5-month payback. For a cash-strapped startup, the fast payback on ads might be better even though the CAC is higher. This calculator lets you compare channels side by side.
Operators Spotting When Unit Economics Break
Your CAC is $200, LTV is $600 (3:1 ratio, great). Then your churn ticks up to 8% and LTV drops to $300. Now you're at 1.5:1—barely breakeven. Six months ago, you were making money on every customer. Now you're acquiring unprofitably. This calculator is your early warning system. Run it monthly and watch the ratio. When it moves, you know something changed, and it's time to investigate.
Tips and Things to Watch Out For
CAC includes more than direct spend. Your founders spending 20 hours/week on sales is a cost. Your customer success manager bringing customers to expansion revenue is a cost. Your free trial infrastructure is a cost. Many businesses underestimate their true CAC by treating only explicit ad spend as acquisition expense. Allocate indirect costs fairly.
Churn assumptions are make-or-break. If you estimate 2% churn but actual churn is 5%, your LTV is half what you calculated. Be conservative with churn estimates, especially early in a product's life. Most new products have higher-than-expected churn. Better to be surprised by lower churn than blindsided by higher churn.
Payback period trumps ratio for cash flow. A 10:1 LTV:CAC ratio is fantastic, but if payback is 18 months, you might run out of cash before you see the profit. Aim for a payback period under 12 months, ideally under 6. A 3:1 ratio with a 3-month payback beats a 5:1 ratio with a 15-month payback.
Segment your customers. A $10,000 CAC on a $500K lifetime-value enterprise customer is a steal. The same $10,000 on a $2,000 lifetime-value SMB customer is insane. Calculate CAC and LTV separately for each customer segment. You might find that SMB is a money pit while enterprise is a goldmine-or vice versa.
Don't lock in on one quarter. One good quarter doesn't mean sustainable unit economics. Track CAC and LTV over at least four quarters. If your CAC is climbing month-over-month (channels get more expensive as you scale), or your LTV is declining (churn ticks up as you grow), you have structural problems to solve.
Gross margin matters. Not all revenue is profit. A $100 ARPU with 90% gross margin contributes $90 to LTV. A $100 ARPU with 30% gross margin contributes only $30. Make sure you're factoring in cost of goods sold, customer support, and hosting costs when calculating the true profit per customer.
*This calculator estimates CAC payback and lifetime value based on the inputs you provide. Actual results vary based on customer behavior, churn acceleration, upsell patterns, and market dynamics. Consult a financial advisor before making large capital investments based on these projections.*
Frequently Asked Questions
What's considered a healthy LTV:CAC ratio?
3:1 is the minimum acceptable ratio for venture-backed companies. It means you're earning three dollars of lifetime value for every dollar spent on acquisition. 5:1 is very good. 10:1+ is exceptional. Below 2:1 means your acquisition is too expensive relative to what customers will ever spend.
How do I calculate CAC if I have multiple customer types?
Calculate CAC separately for each segment. If you spent $100,000 acquiring 50 enterprise customers and 200 SMB customers, don't average them. Figure out how much of that $100K went to enterprise acquisition vs. SMB, then calculate each separately. You'll get a clearer picture of unit economics per segment.
What if my CAC is rising over time?
Rising CAC is a growth problem. As you exhaust easy-to-reach customers, acquisition gets more expensive. You have two options: accept higher CAC if LTV grows faster, or optimize channels to reduce CAC (product-led growth, referrals, content). This calculator will show you when rising CAC breaks your unit economics.
Should I include all overhead in CAC or just sales and marketing?
Just sales and marketing. Overhead-rent, operations, engineering-is fixed and doesn't scale with each new customer. Your unit economics only care about the variable cost to acquire (CAC) vs. revenue generated (LTV). Fixed costs matter for overall profitability but not for the CAC:LTV ratio.
How does churn affect my payback period?
Churn doesn't directly affect payback (that's just CAC divided by monthly profit per customer). But churn heavily affects LTV. Higher churn = shorter customer lifetime = lower LTV. So churn indirectly makes your payback period feel longer because the customer isn't worth as much. Reducing churn by 1% can double your LTV.
What if I'm pre-revenue or my churn is unknown?
Estimate conservatively. For new products, assume 5-10% monthly churn until proven otherwise. Most founders underestimate churn. If you can't calculate CAC yet because you're not acquiring customers, focus on building a product people love first. Unit economics come after product-market fit.
When should I worry about unit economics?
Now. Even if you're pre-revenue, think about your acquisition model and build toward unit economics early. Many startups raise funding assuming they'll "figure out unit economics later"-and they never do. Better to solve this before you're forced to by a board review or a failing capital raise.
Related Calculators
Use the SaaS metrics calculator to track CAC alongside other health indicators like MRR and churn. Check the ad spend ROI calculator if you're trying to optimize specific marketing channels. The pricing calculator helps you understand whether your ARPU is set correctly to support your LTV goals.