LTV CAC Formula: How to Calculate and Read the Ratio

What Is the LTV CAC Formula?

One division, two inputs.

The LTV CAC formula divides customer lifetime value by customer acquisition cost: LTV / CAC = Ratio. If a customer generates $450 in lifetime value and cost $150 to acquire, the ratio is 3:1. That single number tells you whether your acquisition spend is building a business or slowly draining it, but only if both inputs are calculated correctly first.

The formula itself takes ten seconds to write down. Getting LTV and CAC right, on the other hand, is where most of the work lives. Both numbers get calculated wrong more often than they get calculated right, and a wrong input on either side produces a ratio that looks precise while pointing you in the wrong direction entirely.

This guide walks through the formula, a full worked example, and the specific calculation mistakes that distort the result most often. For the broader question of what a healthy ratio looks like by business model and how to fix one that's underwater, see our CAC to LTV ratio guide. This piece stays narrowly focused on getting the calculation itself right.

The stakes are real. Research published by Harvard Business Review found that increasing customer retention by just 5% can increase profits by 25% to 95%, since retention feeds directly into the lifespan and frequency inputs on the LTV side of this formula. Get those inputs wrong and the ratio you're using to guide acquisition budgets is wrong too.

What Is the Exact LTV CAC Formula?

Write it one way, every time.

LTV CAC Ratio = Customer Lifetime Value / Customer Acquisition Cost. Some teams write it as CAC:LTV instead, which inverts the fraction and communicates the same relationship from the opposite direction. Confirm which direction a benchmark or report is using before comparing it to your own number, since a 3:1 LTV:CAC ratio and a 1:3 CAC:LTV ratio describe the identical business.

LTV / CAC = Ratio

That's the whole formula. The two inputs each have their own formula underneath, and that's where accuracy actually gets decided.

Customer Lifetime Value (simple version):

LTV = Average Order Value x Purchase Frequency x Average Customer Lifespan

Customer Acquisition Cost:

CAC = Total Acquisition Spend / Number of New Customers Acquired

Our customer lifetime value formula guide covers three LTV models (simple, historical, predictive) in depth, since the simple version above is a starting point, not the only option. Use the simple model for a quick ratio check and a historical or cohort-based model once you have 12+ months of repeat-purchase data.

How Do You Calculate the LTV CAC Formula, Step by Step?

Four numbers, then one division.

Calculating the LTV CAC formula takes four steps: total your acquisition spend for a period, divide by new customers acquired to get CAC, calculate LTV from average order value times purchase frequency times lifespan, then divide LTV by CAC. Run the calculation over the same time window for both sides, or the ratio compares numbers that don't actually belong together.

Walk through it with a mid-size DTC skincare brand's numbers for one quarter.

Step 1: Total acquisition spend.

Ad spend ($42,000) + creative production ($3,500) + pro-rated marketing salary ($9,000) + tools and software ($1,500) = $56,000

Step 2: Divide by new customers to get CAC.

The brand acquired 400 new customers that quarter.

$56,000 / 400 = $140 CAC

Step 3: Calculate LTV.

Average order value: $68

Purchase frequency: 3.2 times per year

Average customer lifespan: 2.1 years

$68 x 3.2 x 2.1 = $457 LTV

Step 4: Divide LTV by CAC.

$457 / $140 = 3.26:1

That ratio sits inside the 3:1 to 5:1 range commonly cited as healthy for DTC subscription and repeat-purchase brands, per the industry benchmarks in our CAC to LTV ratio guide. A single quarter's ratio is a snapshot, not a verdict. Run the same calculation every quarter and watch the trend, since one good number can mask a slide that started the month before.

The gap between an ad-only CAC and a fully-loaded one, covered in the mistakes section below, changes this same example's ratio by a full point:

Why Does the Same Formula Produce Different Numbers for Different People?

The formula never changes. The inputs do.

Two teams applying the identical LTV CAC formula to the same business can land on ratios that differ by 2x or more, because CAC and LTV each depend on choices, what costs count, what time window applies, whether margin is included, that aren't specified by the formula itself. The formula is not the hard part. Deciding what goes into each side is.

Ask three questions before you trust any LTV CAC ratio, your own or a competitor's:

Is CAC fully loaded? A CAC built from ad spend alone typically undercounts the true cost by 20 to 35%, since it leaves out creative production, tool subscriptions, and marketing salaries. A brand that reports a 5:1 ratio on ad-spend-only CAC might actually sit closer to 3.5:1 once the full cost stack is included.

Is LTV revenue-based or margin-adjusted? The simple LTV formula above produces a revenue number. A margin-adjusted version, covered in our CLV formula guide, multiplies that same figure by gross margin percentage to produce a profit number instead. The two versions of "LTV" for the same customer can differ by 40 to 60% for physical product businesses, and comparing a revenue LTV ratio against a margin-adjusted benchmark, or the reverse, produces a wrong conclusion even though every individual number was calculated correctly.

Do both sides cover the same time window? CAC calculated for this month against LTV projected over three years mixes timeframes that don't belong in the same fraction. Match the acquisition cohort to the LTV window you're using, and hold that window constant every time you recalculate.

What Mistakes Distort the LTV CAC Formula Most Often?

Four errors show up more than any others.

The most common LTV CAC formula mistakes are undercounting CAC by excluding non-ad costs, using a blended ratio that hides channel-level problems, calculating LTV from too short a purchase history, and mixing revenue-based LTV with margin-adjusted benchmarks. Each mistake pushes the ratio in the direction that makes acquisition spend look safer than it actually is.

Undercounting CAC. Ad-spend-only CAC is the single most common error. If you spend $30,000 on Meta and acquire 300 customers, a $100 "CAC" ignores the $12,000 in salaries, tools, and agency fees that also went into acquiring those customers. The fully-loaded number, closer to $140, changes a 4.5:1 ratio into a materially different 3.2:1.

Blending channels into one ratio. A single company-wide ratio can average a 6:1 organic channel with a 1.8:1 paid social channel into a comfortable-looking 3.5:1 blend, hiding the exact channel that's losing money on every customer it brings in. Calculate the ratio per channel before deciding where to scale spend, the same segmentation approach covered in our customer LTV analysis guide.

Short purchase history. Calculating average customer lifespan from 60 or 90 days of data, especially right after a promotional spike, overstates how long customers actually stick around. Use a full 12-month window at minimum, and validate against an 18- to 24-month cohort where the data exists.

Mixing LTV types against a benchmark. A 3:1 target quoted in a benchmark report is usually based on revenue LTV, not margin-adjusted CLV. Comparing your margin-adjusted ratio against a revenue-based benchmark makes a genuinely healthy ratio look artificially weak. Confirm which version of LTV any benchmark is quoting before you hold your own number up against it.

Not sure if your ratio holds up once CAC is fully loaded? Run the numbers with the free CAC calculator. Two minutes. No signup required.

How Is the LTV CAC Formula Different from the CLV:CAC Formula?

Same shape, different numerator.

The LTV CAC formula uses revenue-based lifetime value as its numerator, while the CLV:CAC formula uses margin-adjusted lifetime value instead, multiplying revenue LTV by gross margin percentage before dividing by CAC. Because CLV is a smaller, profit-based number, a CLV:CAC ratio is always lower than an LTV:CAC ratio calculated from the same underlying customer data.

A customer with $650 in revenue-based LTV and a 55% gross margin has a CLV of $357.50. Against a $140 CAC, that's a 4.6:1 LTV:CAC ratio but only a 2.6:1 CLV:CAC ratio, from the same customer, same acquisition cost, same underlying data. Neither number is wrong. They answer different questions: LTV:CAC tells you about revenue efficiency, CLV:CAC tells you about profit efficiency, and the profit version is the one that should set your actual spending ceiling. Our CLV formula guide covers the full margin-adjustment calculation and benchmark table by business model.

How Often Should You Recalculate the LTV CAC Formula?

Monthly, with a rolling window.

Recalculate the LTV CAC formula monthly using 90-day rolling averages for both CAC and LTV inputs, since a single-month snapshot can be skewed by seasonal ad costs or a short promotional spike on either side. A rolling window smooths that noise out while staying responsive enough to catch a real deterioration within one quarter instead of one year.

Quarterly recalculation is common for board reporting, but monthly tracking at the operating level catches problems earlier. Plot CAC and LTV as two separate lines on the same chart rather than watching the ratio alone. A ratio can hold steady for a month or two even while CAC is climbing, if LTV happens to be climbing at a similar pace, and the two lines converging is often visible before the combined ratio moves enough to trigger concern.

Shopify's own guide to customer lifetime value makes a similar point: LTV deserves the same ongoing attention as conversion rate, not a one-time calculation filed away after the first quarter it's run.

Frequently Asked Questions

What is the LTV CAC formula?

The LTV CAC formula divides customer lifetime value by customer acquisition cost: LTV / CAC = Ratio. A customer worth $450 in lifetime value who cost $150 to acquire produces a 3:1 ratio, the benchmark most commonly cited as the target for sustainable acquisition economics across ecommerce and SaaS businesses.

Is LTV CAC the same as CAC to LTV?

They describe the same relationship written in opposite directions. LTV:CAC of 3:1 means a customer returns three times their acquisition cost. CAC:LTV of 1:3 communicates the identical fact from the other side. Confirm which direction a source is using, since the numbers look different even though the underlying relationship is the same.

What LTV should I use in the formula: revenue or margin-adjusted?

Either works, as long as you're consistent and know which one you're using. Revenue-based LTV produces a higher, less conservative ratio; margin-adjusted CLV produces a lower, profit-accurate one. Use the margin-adjusted version when setting an actual spending ceiling, since it already accounts for cost of goods sold.

Why does my LTV CAC ratio look different each time I calculate it?

Usually because an input changed, not the formula. A shorter purchase-history window, a different CAC cost stack, or switching between revenue-based and margin-adjusted LTV can each shift the ratio by a full point or more on the same underlying business. Lock the inputs and time window before comparing calculations across periods.

Can the LTV CAC formula be used for a one-time-purchase business?

It can, but it loses most of its power. For a business with no repeat purchases, LTV collapses to the margin on a single order, and the ratio becomes close to a first-purchase ROAS calculation. The formula gains meaning once customers make repeat purchases, since that's the "lifetime" portion the calculation is actually built to capture.

Keep Reading

• CAC to LTV Ratio: The Metric That Predicts Business Health, full benchmarks by industry and how to fix a ratio that's underwater.
• CLV Formula: How to Calculate Customer Lifetime Value, the margin-adjusted version of the formula covered here.
• Customer LTV Analysis: How to Segment and Act on It, how to break a blended ratio apart by channel and cohort.