The Four Numbers to Set Before October

The most useful hour you will spend on Q4 involves no creative, no offer and no media plan. It is the hour in September when you write down four numbers that describe what your business looks like when nothing unusual is happening. Everything you decide in November is a comparison against those numbers, and brands that skip this step spend peak trading arguing about whether performance is good without any agreed definition of good. This post covers the four baselines, how to derive each one, and what they are for once trading starts.

The four Q4 baselines are new customer acquisition cost, marketing efficiency ratio, contribution margin per order and maximum allowable acquisition cost. Set in September against normal trading, they become the reference points you trade against through peak, when every number moves and nothing looks normal.

Why Does September Matter?

Because it is the last month that resembles normal. Once offers go live and auction costs climb, every figure in your account is distorted by the promotion, the discount depth and a customer mix that has shifted towards people who were going to buy anyway. A baseline taken in that environment is not a baseline, it is a snapshot of an unusual month.

There is a second reason, less obvious. Recording these numbers in September forces the conversation about what you are prepared to accept before anyone is under pressure. Deciding your margin floor calmly in September and deciding it at eleven at night in late November produce very different answers, and only one of them is a decision.

Baseline One: New Customer Acquisition Cost

Total acquisition spend divided by new customers acquired, deliberately excluding returning buyers. The separation matters more than the number itself.

During peak, blended figures improve almost automatically, because a large share of orders comes from people who already know you and need very little persuading. A brand watching blended CAC can therefore see the metric improve while the cost of genuinely new customers climbs sharply, which is the single most common way an acquisition problem stays hidden until January. We set out the measurement approach in our new customer CAC guide, and the broader argument in the blended CAC lie.

Record it as a range rather than a single figure, because September will have good weeks and bad ones, and a range is harder to argue with later.

Baseline Two: Marketing Efficiency Ratio

Total revenue divided by total marketing spend, across everything. MER is the number that survives peak trading intact, because it does not care how platforms attribute conversions to themselves, and during a period when every channel claims the same sale that indifference is the whole point.

Set it as a monthly figure and a weekly one. The weekly version is what you will actually use in November, when a single strong day can make a monthly figure look fine while the trend underneath it deteriorates. The case for reporting against MER rather than platform ROAS sits in our post on MER vs ROAS.

Baseline Three: Contribution Margin Per Order

Revenue per order minus cost of goods, shipping and fulfilment, payment processing and any promotional cost. Not gross margin, and not an aggregate profit figure at the end of the quarter, but the money a single order leaves behind.

This is the baseline that does the most work, because it is the one that moves in ways nobody expects. Revenue can rise, conversion rate can climb, platform ROAS can look excellent and contribution margin per order can still fall, because discount depth rose and the customer mix shifted. A record quarter that loses money is not a paradox, it is an arithmetic outcome, and this number is where it shows up first. The full argument is in our Q4 profit trap piece and the mechanics in our unit economics guide.

Write down the floor alongside the baseline: the margin per order below which you will pull back rather than continue. That sentence, written in September, is what stops a bad week becoming a bad quarter.

Baseline Four: Maximum Allowable CAC

The most you can afford to pay for a customer while still hitting your payback target. It is derived rather than chosen, which is why so few brands have it.

Start with contribution margin per order. Decide how many orders you are prepared to wait for before the customer has paid for themselves, which for most DTC brands is somewhere between the first and the third. Multiply, and you have the ceiling. If your current acquisition cost sits close to that ceiling in September, you have no room to scale in November, and that is worth knowing in September rather than discovering it with a budget already committed.

This number is also what converts retention from a nice idea into a spending permission. A brand whose second order arrives reliably can afford a higher first-order acquisition cost than a brand whose customers do not return, which means retention work done in September directly raises what you can bid in November. The relationship is set out in our LTV guide and our post on cohort payback.

What Are the Baselines Actually For?

They convert judgement calls into comparisons, which is the only thing that works under pressure.

Without them, every Q4 decision is a debate. Is this cost per purchase acceptable? Should we scale? Is the offer working? Everyone has an opinion and the loudest one usually wins. With them, the same questions have answers: acquisition cost is within range of baseline and margin per order is above the floor, so scale; margin per order has been below the floor for three days, so pull back. Decisions made against written references are consistently better than decisions made against a dashboard and a feeling.

They also make the post-season review possible. In February, when you are deciding what to do differently, the only interesting question is how peak compared with normal trading, and you cannot answer it if nobody recorded what normal looked like.

What Does Holding Them Look Like?

Across the client portfolio we run at Webtopia, last Cyber weekend produced revenue growth of more than 60% year on year with blended CPA held flat and triple digit new customer growth. The interesting part is not the growth, it is the flat CPA underneath it. Spend scaled hard and efficiency held, which only happens when the thresholds were agreed in advance and the accounts were built to trade against them rather than react.

That is what baselines buy you. Not a better November, but a November where the decisions are already made and the job is execution.

What Should You Do This Week?

Pull the four numbers for a clean September fortnight. Write them somewhere the whole team can see, with the margin floor and the maximum CAC stated as explicit limits rather than observations. Name the person who checks them, weekly through October and daily through the promotional window. Then leave them alone, because a baseline you revise during peak is not a baseline either.

An hour of work, and it changes every conversation you will have for the next three months.

The Bottom Line

Set new customer CAC, MER, contribution margin per order and maximum allowable CAC in September, while trading still looks normal. Write the floor and the ceiling as limits. Give one person the job of checking them. Everything else in Q4 is a comparison against those four numbers, and brands without them spend the quarter guessing expensively.

Our Biggest Q4 Guide Lands Soon

We are finishing the full Q4 Profit Playbook, including the baseline worksheet and the scorecard we run on client accounts through peak. Our newsletter list gets it first. Join at webtopia.co/newsletter to be first to get it, plus every platform change that matters each Tuesday in Beyond the Clicks.

Want Your Baselines Set Properly?

Book a call and we will work through the four numbers with your own data before October, part of how we work as an ecommerce marketing agency and an ecommerce paid media agency.

Frequently Asked Questions

What are the four Q4 baselines?

New customer acquisition cost, marketing efficiency ratio, contribution margin per order and maximum allowable acquisition cost, set in September against normal trading.

Why set baselines in September rather than during Q4?

Because a baseline taken during a promotional period is not a baseline. September is the last month that resembles normal trading before discounts, higher auction costs and a shifted customer mix distort every figure.

What is maximum allowable CAC?

The most you can afford to pay to acquire a customer while still meeting your payback target. It is derived from contribution margin and repeat purchase behaviour rather than chosen.

Why separate new customer CAC from blended CAC?

Because blended figures during peak are flattered by returning customers. Blended CAC can improve while the cost of genuinely new customers rises, hiding the problem until January.

What does a good Q4 look like against these baselines?

Spend scaling substantially while acquisition cost holds close to baseline and contribution margin per order stays above the floor.

How often should the baselines be checked during peak?

Weekly through October and daily through the promotional window, by one named person.