“Our ROAS is 5x — that’s great, right?” Not necessarily. We’ve audited businesses reporting a 5x ROAS that were losing money on every order, and businesses with a 2x ROAS that were growing profitably. The difference lies in the metrics behind the headline number: margins, returns, repeat purchases and the true cost of acquiring a customer.
This guide explains the performance marketing metrics that actually determine profitability — ROAS, POAS, CAC, LTV and MER — with formulas and worked examples you can apply to your own business.
The metrics at a glance
Widely used industry definitions. A 3:1 LTV:CAC ratio is a common rule of thumb, especially in subscription and SaaS businesses.
ROAS: useful, but incomplete
Formula: ROAS = Revenue attributed to ads ÷ Ad spend
If you spend ₹1,00,000 and ads generate ₹4,00,000 in revenue, your ROAS is 4x. ROAS is valuable for comparing campaigns and channels within the same business. Its weakness is that it ignores costs: product cost, shipping, payment fees, returns and discounts.
Break-even ROAS
To know whether a ROAS is good, calculate your break-even point: Break-even ROAS = 1 ÷ Gross margin %. With a 40% margin after product, shipping and fees, break-even ROAS is 1 ÷ 0.40 = 2.5x. Below that, every sale loses money on the first order.
Break-even ROAS at different gross margins
Calculation: break-even ROAS = 1 ÷ gross margin. A 20%-margin business needs 5x ROAS just to break even on the first order.
POAS: the profit-aware alternative
Formula: POAS = Gross profit from ad-driven orders ÷ Ad spend
POAS replaces revenue with gross profit, so a POAS above 1.0 means ads are paying for themselves on the first order. It is especially powerful for stores with products at very different margins. Two campaigns with identical 4x ROAS can have very different POAS if one sells high-margin products and the other sells discounted low-margin items.
| Campaign | Spend | Revenue | ROAS | Margin | Gross profit | POAS |
|---|---|---|---|---|---|---|
| A: Bestsellers (full price) | ₹50,000 | ₹2,00,000 | 4.0x | 55% | ₹1,10,000 | 2.2 |
| B: Sale collection | ₹50,000 | ₹2,00,000 | 4.0x | 22% | ₹44,000 | 0.88 |
Worked example. Same ROAS, very different profitability — campaign B loses money on the first order.
To optimise for POAS, pass profit (or margin-adjusted values) to Google Ads and Meta as the conversion value, or use custom labels in your product feed to bid differently by margin band.
CAC: what it really costs to win a customer
Formula: CAC = Total acquisition costs ÷ Number of new customers
A true CAC includes more than ad spend: agency fees, creative production, tools and sales costs where relevant. It should also be calculated for new customers only. Platform ROAS often mixes new and returning buyers, which flatters results — returning customers would often have bought anyway.
LTV: the number that sets your ceiling
Simple formula: LTV = Average order value × Gross margin × Average number of orders per customer
If your average order is ₹1,500, margin is 50% and customers order three times on average, LTV is ₹1,500 × 0.5 × 3 = ₹2,250 in gross profit. That is the maximum you could theoretically pay to acquire a customer and break even over their lifetime.
The LTV:CAC ratio
A widely used rule of thumb is that LTV should be around three times CAC. Below 1:1 you lose money on every customer; around 3:1 you have room for overheads and profit; well above 5:1 you may be under-investing in growth. Use the ratio together with payback period — how many months it takes to recover CAC — because cash flow matters as much as long-term value.
MER: the blended reality check
Formula: MER = Total revenue ÷ Total marketing spend
Every ad platform uses its own attribution model, so adding up platform-reported revenue usually exceeds your actual revenue. MER (marketing efficiency ratio) ignores attribution and looks at the whole business. If MER is stable or improving while you scale spend, your marketing is working — regardless of what each platform claims.
Platforms report ROAS. Businesses bank profit. Build your targets from your margins, not from the dashboard.
A practical framework for setting targets
- Calculate true gross margin per order after product cost, shipping, payment fees, packaging and average returns.
- Set a break-even ROAS (1 ÷ margin) and a target ROAS above it.
- Estimate LTV from historical repeat purchase data (use 6- or 12-month LTV if your history is short).
- Define an allowable CAC — for example, LTV ÷ 3 — and a maximum payback period.
- Track MER weekly alongside platform metrics to catch attribution drift.
- Move to POAS bidding once your tracking can pass margin-aware values to ad platforms.
Worked example: setting targets for a D2C brand
Let’s apply the framework to a hypothetical apparel brand.
| Input | Value | Notes |
|---|---|---|
| Average order value | ₹2,000 | From store data |
| Product cost | ₹700 | 35% of AOV |
| Shipping, packaging & payment fees | ₹220 | Including COD charges |
| Average returns cost | ₹180 | Return rate × reverse logistics and write-offs |
| Gross profit per order | ₹900 | 45% contribution margin |
| Break-even ROAS | 2.22x | 1 ÷ 0.45 |
| Orders per customer (12 months) | 2.2 | From cohort data |
| 12-month LTV (gross profit) | ₹1,980 | ₹900 × 2.2 |
| Allowable CAC at 3:1 | ₹660 | ₹1,980 ÷ 3 |
Illustrative calculation using hypothetical numbers.
With these numbers, the brand can afford a new-customer CAC of up to ₹660 while keeping a healthy 3:1 ratio — even though that CAC is below the ₹900 gross profit of a single order. If the brand were more aggressive, it could pay closer to ₹900 and still break even on the first order, relying on repeat purchases for profit. That choice depends on cash flow: the more you pay upfront, the longer your payback period.
Common measurement mistakes
- Using revenue instead of contribution margin to set targets.
- Ignoring returns and RTO, which can wipe out the margin on a large share of orders.
- Counting returning customers in CAC, making acquisition look cheaper than it is.
- Using lifetime value estimates without data — base LTV on actual cohorts, not hopes.
Key takeaway: ROAS tells you which campaigns are efficient. POAS, CAC, LTV and MER tell you whether your business is actually growing profitably. Use all of them.
Frequently asked questions
What is the difference between ROAS and ROI?
ROAS measures revenue per unit of ad spend. ROI measures net profit relative to total investment, accounting for all costs. ROAS is a campaign metric; ROI is a business metric.
What is a good ROAS for e-commerce?
Any ROAS above your break-even point is profitable on the first order. With 40% margins, that’s above 2.5x. Many brands accept lower first-order ROAS if repeat purchases make LTV strong.
What is POAS?
Profit on ad spend — gross profit generated divided by ad spend. A POAS above 1 means ads are profitable on the first order.
How do I calculate customer acquisition cost?
Divide total acquisition costs — ad spend, agency fees, creative and tools — by the number of new customers acquired in the same period.
What is a good LTV to CAC ratio?
Around 3:1 is a common benchmark. Below 1:1 is unprofitable; very high ratios can mean you are under-investing in growth.
What is MER in e-commerce?
Marketing efficiency ratio is total revenue divided by total marketing spend. It provides a blended, attribution-independent view of marketing performance.
Why doesn’t platform-reported revenue match my store revenue?
Each platform uses its own attribution windows and may claim credit for the same sale. Platform totals often exceed actual revenue, which is why blended metrics matter.
Should I optimise campaigns for ROAS or CPA?
Optimise for value (ROAS or POAS) when order values vary significantly; optimise for CPA when each conversion has similar value, as in many lead-generation businesses.
How do I calculate payback period?
Divide CAC by the monthly gross profit a customer generates. The result is the number of months needed to recover acquisition cost.