Your target ACoS is the maximum advertising cost of sales that preserves your desired net margin. You calculate it from your price, your costs and your fees, then use it as the bid goal for your campaigns. For profit-focused sellers, that target should sit at or below break-even ACoS. For sellers chasing growth or launch visibility, a higher figure can make sense for a limited period. The calculator and steps below show you exactly how to find your own number.
TL;DR:
- Sellers should calculate their break-even ACoS based on full costs, including product, fulfillment, and referral fees, to ensure ad spend does not erode profit.
- Using a target ACoS at or below the break-even point helps protect margins, while higher targets may be justified temporarily for launch or visibility campaigns.
- Monitoring TACoS alongside ACoS provides a clearer picture of actual business health, especially when organic sales grow and offset ad costs over time.
- Automating and tracking profit margins at the SKU level using tools like Osellpa can maintain accurate targets and improve campaign efficiency across large catalogs.
- Campaign optimization should focus on search-term hygiene, bid control, listing improvements, and data-driven adjustments to lower ACoS effectively.
Table of Contents
- What ACoS measures and how it compares with ROAS
- How to calculate your break-even ACoS
- How to set a realistic target ACoS
- How to lower ACoS: a tactical checklist
- Why TACoS matters and how it should shift your target
- Making these targets and calculations without the spreadsheet
- Rules of thumb for acceptable ACoS by product stage
- How Osellpa helps you set and hold your target ACoS
- Sources
- FAQ
What ACoS measures and how it compares with ROAS
ACoS stands for Advertising Cost of Sales. It tells you what percentage of the sales generated by an ad campaign went towards paying for that campaign. Amazon’s own guidance defines it as ad spend divided by ad-attributed revenue, converted to a percentage.
The formula is simple:
ACoS = (Ad spend ÷ Ad-attributed revenue) × 100
Say you spend £50 on a campaign and it generates £250 in attributed sales. Your ACoS is (£50 ÷ £250) × 100, which comes to 20%.
ROAS, or Return on Ad Spend, is the inverse view of the same relationship. Where ACoS shows cost as a share of revenue, ROAS shows revenue as a multiple of cost.
ROAS = 1 ÷ (ACoS ÷ 100)
A 20% ACoS converts to a ROAS of 5, meaning every £1 spent on advertising returned £5 in sales.
Neither metric tells you whether a campaign is actually profitable on its own. A few points worth keeping in mind:
- A low ACoS on a low-margin product can still lose money once fees and cost of goods are subtracted.
- A high ACoS on a high-margin product can still leave healthy profit behind.
- ACoS and ROAS measure ad efficiency, not bottom-line profit, so they need to be read alongside your actual margins.
That gap between “efficient advertising” and “profitable advertising” is exactly why break-even ACoS matters more than the raw percentage on its own.
How to calculate your break-even ACoS
Break-even ACoS is the point at which advertising spend exactly cancels out your product profit. Above that line, every additional pound of ad spend eats into margin. Below it, the campaign is still contributing to profit.
To calculate it accurately, you need to know your full cost stack per unit, not just the wholesale cost of the product:
- Cost of goods sold, including manufacturing or purchase price.
- Amazon fulfilment fees, such as FBA pick, pack and storage charges.
- Amazon referral fees, which vary by category.
- VAT or other tax obligations that apply to your business and marketplace, since Amazon’s advertising documentation advises including marketplace fees and fulfilment costs when working out break-even ACoS.
Once you have those figures, the formula is:
Break-even ACoS = (Selling price − Total costs excluding ads) ÷ Selling price × 100
Take a product that sells for £30, with £18 in combined product cost, fulfilment and referral fees. Your pre-ad profit is £12, so break-even ACoS is (£12 ÷ £30) × 100, which equals 40%. Any ACoS above that figure means the campaign is running at a loss on that SKU.
Two caveats worth flagging: costs vary between SKUs even within the same catalogue, so a portfolio-wide average can hide loss-making products, and rounding errors compound quickly when margins are already thin. Calculate break-even at the SKU level wherever you can, not just at the account level.
How to set a realistic target ACoS
Break-even ACoS is your ceiling for pure profitability. Your target ACoS is where you actually choose to operate, and that depends on what you’re trying to achieve.
Three templates cover most situations:
- Profit-first target: set your target ACoS at 60 to 80% of your calculated break-even figure, leaving a buffer for fee changes, returns and seasonal fluctuations.
- Growth-first target: allow ACoS to run close to or slightly above break-even for a defined period, usually during a launch or a push into a new category, accepting short-term losses for ranking gains.
- Hybrid target: set separate targets for “harvest” campaigns on established SKUs (profit-first) and “hunt” campaigns on new keywords or products (growth-first), reviewed on a monthly cycle.
To run the calculation yourself, gather these inputs:
- Selling price on the relevant marketplace.
- Cost of goods, landed cost if importing, and any packaging or prep costs.
- Amazon referral fee percentage for that category.
- FBA or FBM fulfilment cost per unit.
- VAT treatment, since this affects net revenue differently depending on your registration status and marketplace.
Multiply through your break-even formula, then apply the appropriate template percentage. A free target ACoS calculator can speed this up if you’re checking several SKUs at once, since most accept price, margin, cost and fee inputs and return a recommended figure automatically. Internal tools like Osellpa’s PPC optimisation guide walk through the difference between profit-focused and growth-focused bidding in more detail if you want to see the logic applied to live campaigns.
If you sell across multiple marketplaces, don’t assume one target travels well between them. Run the break-even calculation per marketplace, not just per product, and revisit it whenever Amazon changes its fee schedule.
How to lower ACoS: a tactical checklist
Once you know your target, the next question is how to close the gap between where you are and where you want to be. Most ACoS reduction comes from a handful of repeatable actions rather than a single fix.
Campaign structure and match types
- Separate exact, phrase and broad match into their own campaigns so you can control bids independently.
- Move proven converting search terms from broad or auto campaigns into dedicated exact-match campaigns with tighter bids.
Search-term hygiene
- Review the search term report weekly during the first month of a new campaign, then fortnightly once it stabilises.
- Add negative keywords for any search term that has generated clicks without a sale after a reasonable data threshold, typically 10 to 15 clicks with no conversion.
Bid rules and automation
- Automated bid strategies that target a specific ACoS can work well once a campaign has enough conversion history, but they need monitoring rather than being left untouched.
- Set alerts for sudden ACoS spikes so you catch a bid rule misfiring before it burns through a week’s budget.
Listing and conversion improvements
- A listing with weak images, an uncompetitive price or a lost Buy Box will show a high ACoS even with well-optimised campaigns, because the problem sits on the conversion side, not the ad side.
- Improving your main image, tightening your bullet points, and confirming you hold the Buy Box consistently often lowers ACoS faster than any bid adjustment.
Measurement and validation
- Run changes as controlled tests where possible, comparing a week of new settings against the previous week rather than judging on a single day.
- Track TACoS alongside ACoS so you can see whether campaign changes are shifting sales towards organic as well as paid.
Pro Tip: Before cutting a campaign’s budget because ACoS looks high, check whether it’s also driving organic rank gains. Sometimes the “expensive” campaign is doing the most long-term work.
Why TACoS matters and how it should shift your target
TACoS, or Total Advertising Cost of Sale, measures ad spend against your total sales, both organic and paid, rather than against ad-attributed sales alone. Where ACoS only sees the slice of revenue advertising directly caused, TACoS shows how advertising is affecting your business overall.
TACoS = (Ad spend ÷ Total sales) × 100
This matters because a campaign can carry a high ACoS while still doing its job, if it’s pulling in organic sales through improved ranking. A new product with no reviews and no organic visibility may need an ACoS well above break-even for the first few weeks, and that’s acceptable if TACoS is falling as organic sales pick up the slack.
A practical way to use this: track TACoS over a 90-day window rather than day to day. If your ACoS stays elevated but your TACoS trends downward over that period, organic sales are growing and taking pressure off paid campaigns, which is the outcome you want. Osellpa’s own TACoS explainer covers this shift in more depth, including how to decide when it’s time to move from a growth target back to a profit target.
- Favour TACoS as your primary metric when you’re building a new brand or pushing into a competitive category.
- Favour ACoS as your primary metric once a product is established and your goal is margin protection rather than rank building.
Making these targets and calculations without the spreadsheet
Calculating break-even ACoS by hand works for one SKU. It becomes unmanageable across a catalogue of fifty or five hundred, especially when fees, costs and prices shift regularly.
Any tool built for this job needs a few core capabilities:
- Per-SKU break-even calculations that update automatically when costs or fees change.
- Campaign-level ACoS dashboards that sit next to profit data, not in a separate report you have to cross-reference manually.
- Automated negative keyword rules that flag or remove non-converting search terms without waiting for a weekly manual review.
Osellpa builds its platform around this exact gap. It connects directly to Amazon’s API for profit tracking, runs automatic and manual PPC optimisation, and reports both ACoS and true profit per SKU in the same dashboard rather than forcing sellers to reconcile spreadsheets.
Osellpa reports that sellers using its optimisation and tracking tools see up to a 20% increase in sales after implementation. That figure comes from the platform’s own user outcomes, so treat it as a claim from the provider rather than an independent benchmark, and check it against your own results.
Whichever tool you evaluate, run it through the same checklist:
- Confirm how frequently it syncs with Amazon’s API, since stale data produces stale targets.
- Check whether margin calculations happen at SKU level or only at account level.
- Look for audit logs or export options so you can verify automated bid changes manually if something looks off.
Rules of thumb for acceptable ACoS by product stage
A launch listing with no reviews and no ranking history can often tolerate ACoS above break-even during an initial period, because the goal is visibility, not margin. A growth-stage product with some organic traction should sit closer to break-even, tightening as ranking improves. A mature, stable seller should treat break-even as a firm ceiling and aim for a target 20 to 40% below it wherever competition allows.
Whatever stage you’re in, give changes enough time to show real signal. A week of data on a low-volume keyword tells you very little. Wait for a meaningful number of clicks before adjusting bids, and set a rollback point in advance, so you’re not tempted to keep a losing test running because it “might turn around.”
Judge SKUs individually rather than trusting a portfolio average. Averages hide the products quietly losing money underneath the ones performing well.
— Harry
How Osellpa helps you set and hold your target ACoS
Working out a target ACoS by hand is manageable for a handful of products. Keeping it accurate across a full catalogue, with fees and costs shifting every quarter, is a different job entirely. Osellpa’s profit tracking and PPC optimisation tools handle that recalculation automatically, tying campaign ACoS directly to per-SKU margin so you can see, at a glance, which campaigns are within target and which have drifted past break-even.
The platform connects directly to Amazon’s API, which means your profit and advertising figures update from your actual account data rather than a spreadsheet you update once a month. Plans run from £10 a month on the Launch tier through to £40 a month on the Advanced tier, with annual pricing available on the pricing page for sellers who want to commit for the year.
If you’d rather see the numbers on your own campaigns first, Osellpa’s free PPC bid optimisation report gives you a breakdown of where your current spend sits against your break-even ACoS before you commit to anything.
FAQ
What should my ACoS be on Amazon?
There’s no single correct ACoS for every seller, since it depends on your margin, category and goals. Calculate your break-even ACoS from price, costs and fees, then set your target below that figure for profit-focused campaigns or closer to it during a growth phase.
What ROAS is 25% ACoS?
That means every £1 of ad spend returned £4 in attributed sales.
Is it better to have a high or low ACoS?
Neither is inherently better outside the context of your margins and goals. A low ACoS on a thin-margin product can still be unprofitable, while a higher ACoS on a high-margin or newly launched product can be a reasonable trade-off for growth.
How do I calculate ACoS in Amazon?
Divide your total ad spend by the ad-attributed revenue it generated, then multiply by 100 to get a percentage, as Amazon’s own definition sets out. For example, £50 in spend against £250 in attributed sales gives an ACoS of 20%.
