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Savvy PPC marketers often praise LTV:CAC as a superior KPI for measuring profitability and guiding budget decisions. 

While insightful, correctly leveraging LTV:CAC is far more complex than it seems – and certainly not as straightforward as ROAS, which itself can be misleading.

To avoid missteps, it’s crucial to understand when LTV:CAC is useful, its limitations, and how a poorly calculated metric can lead you to the wrong north star. 

If your agency recommends increasing your PPC budget based on a “great” LTV:CAC ratio, be cautious. There may be critical nuances (or even conflicts of interest) at play.

This article breaks down the fundamentals of LTV:CAC, including:

• What LTV:CAC is and why it’s important.
• Common pitfalls when using the metric.
• How to refine LTV:CAC, plus alternative KPIs.

What is LTV:CAC?

LTV:CAC (customer lifetime value to customer acquisition cost) measures the relationship between the value a customer brings to a business over time and the cost of acquiring that customer. It’s calculated as:

• LTV:CAC = LTV / CAC

This ratio helps businesses assess whether their customer acquisition efforts are profitable. 

A higher LTV:CAC indicates that customers generate more revenue than their acquisition cost, while a lower ratio could signal inefficiency or unprofitable marketing.

Breaking down the components

LTV (customer lifetime value) represents the total revenue a customer generates throughout their relationship with a business.

Formula: 

• LTV = (Average order value x Total transactions) / Unique customers

CAC (customer acquisition cost) is the average cost incurred to acquire a new customer within a specific period.

Formula: 

• CAC = Total marketing costs / Number of new customers

Note: Always calculate both metrics using the same time period to avoid skewed results.

Why is LTV:CAC important – and how can it be dangerous?

LTV:CAC serves one core purpose: ensuring profitability. 

This KPI is critical for a company’s future because it measures whether the value generated from newly acquired customers justifies the cost of acquiring them.

It’s often compared to return on ad spend, or ROAS, (revenue generated by ads / ad costs) but goes a step further. 

While ROAS focuses on immediate returns, LTV:CAC considers the long-term revenue potential of a customer. 

This broader view can encourage marketers to lower ROAS targets and increase budgets, assuming future revenue will balance acquisition costs over time.

For example, imagine a marketer spends $30 to acquire a new customer who generates $30 in immediate revenue (100% ROAS). 

Based on historical data, the finance team predicts that this customer will make three additional purchases of $30 each, totaling $120 in revenue over their lifetime.

• Total revenue = $30 (initial purchase) + 3 x $30 = $120
• LTV = $120
• CAC = $30
• LTV:CAC = $120 / $30 or 4:1

This 4:1 ratio might suggest strong profitability and justify increased spending.

However, it can be dangerous.

Profitability metrics like LTV:CAC often require deeper financial oversight, yet marketers may lack visibility into key cost components, such as payback periods, retention variability, and operational costs. 

Misunderstanding these factors can lead to overestimations of profitability and misguided budget increases.

Let’s break down some of the common traps that make LTV:CAC a potentially misleading metric.

Dig deeper: 5 KPIs to measure paid media success and 5 to measure business success

7 common pitfalls of using the LTV:CAC ratio

1. Ignoring the impact of customer retention

LTV:CAC is often praised by top marketers as a superior KPI, which might tempt you to adopt it too. 

While it can be valuable in scenarios with high retention and repeat purchase rates (like SaaS), it’s not always reliable.

Before using LTV:CAC, run a retention analysis to answer: “How many times do my customers purchase on average over a set period?”

In ecommerce, customer retention is typically around 30% at best. 

Using the earlier ROAS example, if you spend $30 to generate $120 in revenue (400% ROAS), you might assume retention will increase total revenue by 30%, raising it to $156. This would suggest a higher 520% ROAS.

While appealing, it’s far from transformative enough to justify dramatically increasing your budget. 

2. Overlooking payback period and cash flow

Even if your retention is strong enough to justify using LTV:CAC as your north star metric and your ratio slightly exceeds the standard 3:1, increasing your PPC budget blindly can be risky.

Why? Because LTV:CAC doesn’t account for the payback period – the time required to recover CAC expenses, or how long it takes for revenue to break even with acquisition costs.

If your payback period is 12 months, customers won’t become profitable until the 12-month mark. 

During that time, your balance sheet remains negative, putting strain on cash flow and limiting your ability to reinvest in PPC campaigns or other growth strategies.

To scale faster, you need cash on hand since existing funds are already tied up in customer acquisition. 

Options include raising capital or improving fundamentals (e.g., lowering CAC, raising prices, or encouraging prepayment).

Bottom line: A positive LTV:CAC doesn’t guarantee you can safely scale your budget.

3. Misunderstanding marketing LTV vs. finance LTV

Marketers often calculate LTV using basic metrics like revenue – sometimes even pre-tax figures – resulting in inflated and misleading values. 

Naturally, both LTV and CAC should accurately reflect the balance sheet, but this is where many marketers go wrong.

Finance teams often step in to correct these calculations, which can lead to uncomfortable conversations if marketers lack financial literacy. 

To avoid this, marketers need to understand finance-level metrics and how their stakeholders calculate profitability.

LTV is fundamentally a finance KPI. Some finance teams calculate it using gross profit margin (COGS), while others factor in operating expenses (OPEX), making it closer to an EBIT-based KPI.

Ultimately, it’s not about challenging their process but aligning with it. 

To collaborate effectively, marketers should understand key cost components like:

• Support.
• Infrastructure.
• Materials (for physical products).
• Sales and marketing expenses.
• Development costs.
• Other operational expenses.

By aligning with finance teams and using accurate metrics, LTV:CAC can become a far more reliable KPI.

Dig deeper: 3 PPC KPIs to track and measure success

4. Miscalculating CAC by ignoring non-marketing customer sources

PPC, marketing, and other customer sources are critical when assessing CAC and its impact on LTV:CAC. 

Lowering CAC is an obvious way to improve the LTV:CAC ratio, but it can complicate calculating CAC accurately.

A common issue is calculating CAC by dividing total marketing costs by total new customers, disregarding other customer sources. 

In some businesses, where marketing drives about 95% of customer acquisition, this approach might not significantly affect the LTV:CAC ratio and simplifies the calculation.

However, this often overlooks non-marketing customer sources like word of mouth, viral organic content, or baseline growth.

This inflates the customer count, artificially lowering CAC and boosting LTV:CAC, creating a misleading impression of growth.

In the long run, this can lead to structural issues.

While some argue that word of mouth stems from branding or top-of-funnel campaigns, this is only sometimes true.

Many customer sources, such as referral programs, sales initiatives, or product-driven growth, are independent of traditional marketing or PPC efforts.

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5. Assuming all customers are equal

Assuming all customers are equal can lead to inflated LTV:CAC ratios and dangerous strategies. 

You might attempt to boost LTV and make LTV:CAC look better quickly, but this approach can be misleading.

A common mistake is calculating LTV as total revenue divided by total customers over a period, creating an average that hides differences between customer segments. 

Not all customers contribute equally in terms of revenue and retention.

For instance, if the average LTV is $480, it likely doesn’t reflect the actual distribution of customer value:

• 60% of customers spend around $280.
• 30% of customers spend around $600.
• 10% of customers spend around $1,300.

If you aim for a 3:1 LTV:CAC ratio based on the $480 average LTV, you would set a target CAC of $160. 

However, for 60% of your customers, who only generate $280 in LTV, the sustainable CAC should be $93 ($280/3). 

This highlights a significant gap, as the average target would be too high for most customers.

Additionally, the top 10% of customers with a $1,300 LTV likely aren’t acquired through marketing, which complicates the calculation further.

Bottom line: Targeting a $160 CAC could be harmful. Focus on increasing LTV through targeted PPC efforts.

6. Disregarding changes in LTV fundamentals

The purpose of LTV:CAC is to validate marketing investments, assuming that both CAC and LTV are accurately predictable. 

However, these metrics can fluctuate significantly.

Consider a more advanced formula for LTV:

• LTV = Monthly recurring revenue x Growth profit margin / Monthly cancellation rate

Each of these components is dynamic and depends on the company’s ability to maintain or improve its fundamentals:

• MRR: Can you cross-sell or upsell effectively?
• GPM: Can you enhance overall efficiency?
• Cancellation rate: Are new competitors entering the market? Is the market shrinking?

For example, HubSpot reportedly tripled its LTV in just 18 months. Now, imagine a smaller company experiencing the opposite trend.

Bottom line: LTV is a forecast, not a certainty. Don’t place too much confidence in LTV or your LTV:CAC ratio.

7. Treating LTV as a strategy

While this might seem slightly off-topic for PPC practitioners, it’s crucial to grasp when collaborating with stakeholders.

Holding the LTV flag high without fully engaging with others can lead to issues.

Imagine you secure additional budget for performance marketing – great news! 

But as spending increases, CAC rises, making the LTV:CAC ratio worse. 

In response, you might raise prices to boost LTV.

Problem solved?

Not quite.

Higher prices may lead to increased monthly cancellations. Even worse, the new customers acquired with that extra budget might be of lower quality, spending less and churning faster.

The customer support team steps in, confident they can resolve these issues by expanding their efforts, which increases costs and strains cash flow.

This scenario highlights how LTV is deeply interconnected with various aspects of the business. 

Mistaking this metric for a stand-alone strategy can lead to missteps. It’s essential to use LTV as a tool, not a strategy in itself, to ensure sustainable growth.

How to ‘fix’ LTV:CAC, plus alternative KPIs

LTV:CAC can be a useful metric, but its complexity and potential for misinterpretation mean it requires careful handling. 

To make the most of this KPI and ensure it accurately reflects your business’s health, consider the following tips.

Low retention? Don’t use LTV:CAC

In ecommerce, if your repeat purchase rate is around 30%, LTV may not be a relevant metric from a marketing perspective. 

Instead, focus on CAC alone and aim to be profitable from the first order. 

This approach, though tougher, is more sustainable and reflective of genuine growth – think ROAS.

Improve retention through upselling, cross-selling, customer support, or product enhancements.

Dig deeper: How to analyze PPC performance metrics

Collaborate with finance

If using LTV makes sense, build a strong relationship with your finance team. 

Understanding their perspective will help you grasp why certain LTV targets are set. 

To achieve this:

• Learn key financial terms.
• Schedule regular alignment meetings.
• Use agreed-upon data sources to avoid conflicts.

Never report on LTV:CAC alone

Because LTV:CAC encompasses multiple variables, it’s not a standalone metric. 

Include core components like cancellation rate and MRR in your reports. 

This clarity will help identify which components have shifted and guide your next steps. 

Remember, LTV and CAC are dynamic, not fixed.

Segment by customer groups

Segmenting your customer base allows you to pinpoint areas for improvement and identify which customers to exclude. Consider:

• Calculating LTV over different timeframes (30 days, 90 days, 12 months).
• Segmenting customers by cohorts, behavior, and profitability.
• Differentiating between PPC, organic, and non-marketing customers.

Use LTV:CAC wisely

LTV:CAC is valuable for comparing PPC channels and marketing programs, but it’s a complex measurement tool. 

To avoid potential pitfalls, make sure to:

• Conduct a retention analysis before relying on LTV:CAC.
• Partner with your finance team to align on metrics.
• Always segment customers, sources, and micro-KPIs.

Dig deeper: The fallacy of CTR as a KPI: Redefining PPC ad success

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