Business Metrics & KPIs · CAC, LTV, ROAS, Churn & Payback

Platform metrics (Google Ads' click-through rate, Meta's engagement rate, LinkedIn's impressions) measure how well content performs within a platform's system — they optimise for the platform's objectives. Business metrics measure whether marketing investment is generating profitable, sustainable returns for the business.

The gap between platform metrics and business performance is real and consequential. A Google Ads campaign with a low cost-per-click and high CTR may be acquiring users who have low lifetime value and high churn — making the campaign economically unprofitable despite excellent platform metrics. A social campaign with low engagement rates may be generating a small number of high-LTV enterprise customers — making it highly valuable despite weak platform metrics. Without business metrics, you are optimising for the wrong targets.

Customer Acquisition Cost is the total cost of acquiring one new customer, including all marketing and sales costs divided by the number of new customers acquired in the same period.

CAC = Total marketing and sales spend ÷ Number of new customers acquired

What to include in "total marketing and sales spend": paid advertising spend across all channels; agency or freelancer fees; marketing team salaries (at least the proportion of time spent on acquisition activities); software and tools used for marketing; content production costs. Excluding staff costs from CAC calculation dramatically understates the true cost of acquisition — particularly for businesses with large marketing teams.

Blended vs channel-specific CAC

Blended CAC (total cost ÷ total customers) gives an overall efficiency measure but hides channel-level variation. Channel-specific CAC (cost of a specific channel ÷ customers attributed to that channel) reveals which channels are more or less efficient. For budget allocation decisions, channel-specific CAC is more actionable — it identifies which channels to scale (low CAC) and which to scrutinise or reduce (high CAC).

New customer CAC vs total CAC

CAC should only count new customers in the denominator — customers acquired for the first time. Revenue from existing customers (repeat purchases, renewals, expansions) is not an acquisition — including it understates CAC. Some businesses calculate a "blended CAC" including all orders, but this obscures the true cost of growing the customer base.

Customer Lifetime Value is the total net revenue expected from a customer over their entire relationship with the business. LTV sets the ceiling on how much it is rational to spend to acquire a customer — spending more than LTV on acquisition is structurally unprofitable.

Historical LTV (simple)

Historical LTV = Average order value × Average purchase frequency × Average customer lifespan

Example: an e-commerce business with average order value of £80, customers who purchase 3 times per year, and an average customer lifespan of 2 years has an LTV of £80 × 3 × 2 = £480.

Gross margin-adjusted LTV

Revenue-based LTV is incomplete — it does not account for the cost of goods sold or service delivery. Gross margin-adjusted LTV is more accurate for profitability analysis: LTV = Average gross profit per customer × Average customer lifespan. If the business above has a 40% gross margin, gross margin-adjusted LTV = £192 (£480 × 40%). This is the figure to compare against CAC.

Predictive LTV

For businesses with enough historical data, predictive LTV uses statistical models (cohort analysis, survival analysis, or machine learning) to estimate the future revenue a current customer is likely to generate based on their behaviour patterns to date. GA4 generates predictive LTV estimates in its predictive audiences feature — using machine learning trained on historical purchase patterns.

The LTV:CAC ratio compares customer lifetime value to the cost of acquiring that customer. It is the primary indicator of whether a business's marketing economics are sustainable.

CAC Payback Period is the number of months it takes for the gross profit from a customer to recover the CAC — the break-even point on the acquisition investment. CAC Payback = CAC ÷ Monthly gross profit per customer.

A 12-month payback period means the business recoups the cost of acquiring a customer in 12 months and begins generating net positive returns in month 13. For a subscription business with a 2-year average customer lifetime, a 12-month payback means 12 months of positive contribution before each customer churns — reasonable. For a business with a 6-month average lifetime, a 12-month payback means the business never recoups its acquisition cost on average.

Shorter payback periods are better — they reduce the time the business is cash-flow negative on customer acquisition and allow more rapid reinvestment of recovered capital into further acquisition. Payback period under 12 months is generally considered healthy for B2B SaaS; under 6 months is excellent; over 24 months indicates structural acquisition cost or retention problems.

ROAS measures the revenue generated per unit of advertising spend. ROAS = Revenue from ads ÷ Advertising spend. A ROAS of 4 means £4 of revenue for every £1 spent on advertising.

Setting appropriate ROAS targets

A ROAS target is only meaningful when it accounts for gross margin. A 4× ROAS on a business with 25% gross margin means: £4 revenue − £3 cost of goods = £1 gross profit − £1 ad spend = £0 net. Break-even. The minimum profitable ROAS is: Minimum ROAS = 1 ÷ Gross margin percentage. A business with 25% gross margins needs at minimum 4× ROAS just to break even on the direct product cost — before overhead, shipping, support, or other operating costs. Add operating cost coverage to set a true minimum profitable ROAS target.

ROAS limitations

ROAS attributes revenue only to the advertising channel that last touched the user — it does not account for the full conversion journey. A paid search campaign that captures users who were already going to buy (branded search terms) will show extremely high ROAS without generating much incremental revenue. A prospecting campaign generating new customer awareness shows lower ROAS but may be creating future customers who convert later through a different channel. ROAS as a standalone metric favours last-touch channels; for full channel evaluation, combine ROAS with LTV analysis and incrementality testing.

Churn rate measures the proportion of customers (or revenue) lost in a given period. For subscription businesses, churn directly determines LTV and the sustainable economics of the entire business model. Customer churn rate = (Customers lost in period ÷ Customers at start of period) × 100%.

Customer churn vs revenue churn

Customer churn counts the number of customers who cancel. Revenue churn counts the revenue lost from cancellations and downgrades, net of revenue gained from upgrades and expansions. Revenue churn (also called net revenue retention or dollar churn) is more meaningful for businesses with variable customer contract values — losing 10 small customers while gaining $10,000 from one enterprise expansion is positive net revenue retention despite positive customer churn.

Annual vs monthly churn

A monthly churn rate of 3% sounds modest but is equivalent to an annual churn of approximately 31% — losing nearly a third of the customer base per year. Be precise about the measurement period when comparing churn rates, and convert all churn rates to the same period (typically annual) for meaningful comparison.

Monthly Recurring Revenue (MRR) is the predictable monthly revenue from subscriptions — the normalised monthly value of all active subscription contracts. Annual Recurring Revenue (ARR) is MRR × 12. These are the primary revenue metrics for subscription and SaaS businesses because they represent stable, predictable revenue rather than one-time transaction revenue.

MRR movement breakdown

Tracking MRR movement by component reveals the specific levers to optimise: is growth being limited by low new MRR acquisition? By high churn? By low expansion? Each has a different solution — and knowing which problem is dominant is the first step to solving it.

An effective marketing metrics dashboard shows the business metrics that drive decisions — not every available number. For most marketing teams, a monthly dashboard covering:

• CAC (blended and by primary channel) vs previous period and target
• LTV:CAC ratio vs previous period and target
• ROAS by paid channel vs target
• New customers acquired vs target
• Churn rate (monthly) vs previous period
• MRR/ARR and month-over-month growth (for subscription businesses)
• Social-attributed pipeline (from CRM) vs target

Build this dashboard in Google Looker Studio (connecting GA4 data and a CRM data source) or in a shared spreadsheet updated monthly from CRM and analytics exports. The dashboard should be visually clear — trend lines for each metric showing month-over-month direction — and directly actionable: any metric trending in the wrong direction should immediately prompt a specific investigation question.

• Calculating CAC without including staff costs. A marketing team of 5 people costing £250,000 per year is a marketing cost. Excluding team salaries from CAC dramatically understates the true cost of customer acquisition and creates the false impression of higher efficiency than actually exists.
• Using revenue LTV instead of gross margin LTV. LTV:CAC ratios calculated on revenue rather than gross margin overstate how favourable the unit economics are. A 5:1 LTV:CAC ratio based on revenue is 1.5:1 based on gross margin for a business with 30% margins — not a comfortable position.
• Optimising ROAS without reference to LTV. Campaigns optimised for last-touch ROAS targets can exclude the awareness and consideration-stage campaigns that generate the highest-LTV customers — because those customers convert through a different channel's "last click." ROAS optimisation without LTV context can reduce long-term customer quality while improving short-term efficiency metrics.
• Not separating new customer CAC from returning customer revenue. A business where returning customers make up 60% of revenue can look like it has low CAC — because 60% of conversions cost nothing to acquire (they already exist as customers). Separating new customer acquisition metrics from existing customer revenue is essential for understanding the true cost of growth.