An affordable expected CPC equals revenue per order × expected order conversion rate × target ACoS. Use decimal percentages in the formula. This gives an economic estimate, not a guaranteed auction price or a promise that every click will convert.

1. Set the advertising allowance

Calculate contribution before advertising on the same revenue basis as your ad report. Subtract the contribution you want to retain after ads. The remainder is the affordable advertising cost per order.

Hypothetical product: £40 revenue, £24 variable costs and £6 desired contribution after ads. Contribution before ads is £16; advertising allowance is £10. Target ACoS is £10 / £40 = 25%. Review tax, fees, discounts and returns before using your own figures.

2. Estimate conversion with uncertainty

Use mature orders divided by clicks from relevant traffic. A new product may have little evidence; use a range and an explicit learning budget rather than an unsupported category average. A hundred clicks can still leave considerable uncertainty, especially when orders are rare.

Assumed CVR	Calculation with £40 revenue and 25% target	Affordable CPC
5%	40 × 0.05 × 0.25	£0.50
8%	40 × 0.08 × 0.25	£0.80
12%	40 × 0.12 × 0.25	£1.20

These are illustrative assumptions, not UK category benchmarks. Compare traffic with similar intent and separate branded queries from prospecting.

3. Translate the estimate into campaign settings

The entered bid is only one input. Placement modifiers and dynamic bidding can change the effective auction bid. Review them together and choose a base bid whose possible exposure fits your limit. Do not assume Down Only prevents placement adjustments from raising the effective bid above the entered base. Amazon bidding guidance.

A bid below the economic estimate may buy too little traffic to learn; a bid above it may be uneconomic. Decide how much uncertainty you can afford, set a bounded spend limit and retain the old settings.

4. Review with a consistent denominator

Wait for the relevant conversion window and reporting delay before interpreting recent orders as final. Record report type, dates and export time. Amazon conversion metrics.

Hypothetical review: one period has 200 clicks, 16 orders, £140 spend and £640 sales. A second comparable period has 300 clicks, 24 orders, £225 spend and £960 sales. Combined totals are 500 clicks, 40 orders, £365 spend and £1,600 sales. CVR is 8%, average CPC £0.73, and ACoS 22.8125%. Calculate from totals, not an unweighted average of the two ACoS values.

If conversion deteriorates, inspect retail changes and query mix before repeatedly cutting bids. If ACoS is below target, evaluate contribution and capacity before expanding; spare target headroom is not an obligation to spend.

Copyable calculation template

Paste this TSV into a spreadsheet. The formulas assume this header is row 1 and the example is row 2. It is a calculation sheet, not an Amazon bulk-upload file.

Revenue	Variable_costs	Desired_contribution	Expected_CVR	Target_ACoS	Affordable_CPC
40	24	6	0.08	=(A2-B2-C2)/A2	=A2*D2*E2

Format columns D and E as percentages. Require positive revenue and a CVR between zero and one. If costs plus desired contribution exceed revenue, there is no positive advertising allowance under the assumptions.

Can I use this for automatic targeting?

The economic principle still applies, but different targeting groups can have different conversion rates. Do not assume one estimate describes every group.

What changes after a discount?

Recompute revenue, fees, contribution and the plausible conversion range. See price and stock synchronization and ACoS, ROAS and TACoS.

Related Arctavia resources

Use these supporting pages to compare Amazon PPC operating models and implementation choices.

• Amazon Ad Rejections: Check Claims, Images and Destinations
• Amazon Ads ACoS Suddenly Increased: What to Check First
• Amazon Ads ML Bid Review: Guardrails Before Aggression
• Amazon PPC Automation: Data, Decisions and Operating Controls
• Amazon PPC Automation Migration Checklist
• Amazon PPC Automation vs Agency: Which Operating Model Fits Better?