What Is Cost Per Acquisition (CPA) and How Do You Reduce It?

Cost per acquisition — often shortened to CPA — is one of the clearest measures of marketing efficiency available. It tells you how much money, on average, you spend on marketing to bring in one new customer or lead. If you spent £2,000 on ads last month and gained forty new customers, your CPA was £50.

Understanding your CPA is essential for deciding which marketing channels are worth investing in, how to allocate your budget between campaigns, and whether your marketing is actually profitable. A CPA that is lower than the value a customer brings to your business means your marketing is working. One that is higher means you are losing money on acquisition and need to make changes.

Calculating your CPA accurately

The formula is straightforward: divide your total marketing spend by the number of acquisitions it produced. What counts as an acquisition depends on your goal. For e-commerce businesses it is usually a completed purchase. For service businesses it might be a qualified enquiry or a booked consultation. Define this clearly before you calculate, and apply the same definition consistently.

The tricky part is attributing the right spend to the right acquisitions. Multi-channel marketing — where someone might see a Facebook ad, then a Google ad, then receive an email before converting — makes attribution messy. Most businesses use last-click attribution by default, which credits the final touchpoint before conversion. This can undervalue awareness channels like display and social. Consider moving to a data-driven attribution model if your analytics platform supports it.

Track CPA at campaign and channel level, not just overall. Your Google Ads campaigns might have a CPA of £30 while your social media campaigns run at £90. Without this granularity you cannot make informed decisions about where to invest more and where to cut back.

Tactics for reducing your CPA

The most direct way to reduce CPA is to improve your conversion rate. If your ads are generating visits but those visits are not converting, changing your bids or targeting will only move costs around — you need to fix the landing page, the offer, or the checkout process. A conversion rate that doubles from two to four percent halves your CPA without changing your ad spend at all.

On the paid search side, tightening your targeting is usually the next lever. Negative keywords — terms you tell the platform not to show your ads for — eliminate irrelevant clicks that spend budget without converting. Dayparting (restricting when your ads show) and device bid adjustments (reducing bids on mobile if mobile users rarely convert) can also bring CPA down meaningfully.

For any channel, testing your creative regularly prevents performance decay. Ads fatigue over time and their CPA creeps upward as the audience becomes desensitised. Refreshing ad creative every four to six weeks keeps performance from drifting in the wrong direction.

CPA targets and how to set them

A CPA target should be based on the value a customer brings your business. If the average customer spends £500 with you and generates a gross margin of 40 per cent, your gross profit per customer is £200. A CPA below £200 means your marketing is profitable; above it means you are subsidising each customer from other revenue.

For businesses with high lifetime customer value — a solicitor, an accountant, a building company — a CPA that looks high in isolation may still be excellent value. Someone who spends £5,000 a year with you for five years is worth a very different acquisition cost from someone who makes a single £40 purchase.