ROAS vs POAS: which metric to use?

Two eCommerce campaigns can report the same ROAS but have very different POAS. Product cost, discounts, payment fees, shipping, and returns create that difference.

ROAS gives you a quick view of revenue from advertising. POAS adds the margin layer that eCommerce teams need for product and campaign decisions. This guide explains both formulas and shows how to use the ROAS Calculator by Stape to plan your next tracking step.

Return on Ad Spend (ROAS) shows how much revenue your ads produce for each dollar spent on them. The ROAS definition uses two numbers from the same period and within the same attribution scope.

You can report the result as a ratio or a percentage.

For example, an eCommerce store spends $10,000 on ads and attributes $50,000 in revenue to those ads.

This means that each $1 in ad spend produced $5 in recorded revenue.

ROAS helps you compare campaigns, channels, products, and periods. It is also used as a target for value-based bidding in platforms such as Google Ads.

The metric has an important limit. Revenue says nothing about the cost of the products sold. ROAS also leaves shipping, payment fees, discounts, returns, and other order costs outside the formula.

For a useful ROAS comparison, keep these inputs consistent:

POAS stands for Profit on Ad Spend. You may also see the phrase Profit Over Ad Spend. Both names describe the same marketing metric.

POAS shows how much profit your ads produce for each $1 spent on advertising.

To calculate POAS, start with revenue from sales linked to your ads. Remove discounts, canceled orders, returns, taxes, product costs, and order costs. Do not remove ad spend yet. Divide the amount left by ad spend.

For example, a campaign produces $50,000 in revenue. Product and order costs total $35,000, so $15,000 remains. Ad spend is $10,000.

This means each $1 spent on ads produced $1.50 after product and order costs. After the $1 ad cost is covered, $0.50 remains.

A POAS of 1.0 is the advertising break-even point. At 1.0, the contribution profit covers the ads, with nothing left for fixed costs or final profit. Your business target, therefore, needs to sit above 1.0, with the exact level based on your fixed costs and profit goal.

ROAS and POAS use the same denominator, ad spend. The numerator changes from revenue to contribution profit.

The ROAS vs POAS difference matters most when your products have varied margins. A campaign that sells expensive, low-margin products can show strong ROAS and weak POAS. Another campaign can bring less revenue and leave more profit.

POAS also needs a clear internal definition of profit. One team can subtract only the cost of goods sold. Another can include payment fees, and expected returns. Choose one calculation with your finance team and use it across every campaign and period.

Let's study two campaigns with the same $10,000 ad spend.

Campaign A generates more net revenue for the same ad spend, so it has the higher ROAS. However, product and order costs take a larger share of its revenue. Campaign B has the higher POAS because more remains after these costs for each $1 spent on ads.

After ad spend is deducted, Campaign A leaves $5,000 and Campaign B leaves $10,000. Fixed business costs still need to be paid from these amounts.

Use this comparison before deciding where to spend more. Check actual ad spend to see how much budget each product or campaign receives. Then check ROAS and POAS together: a campaign that brings in more revenue per ad dollar does not always leave more profit after costs.

The free ROAS Calculator by Stape helps you plan the possible impact of server-side tracking. It asks for ad spend and conversions, then returns a CPA and a savings scenario in seconds.

Use numbers from the same month and the same advertising scope.

1. Enter the total of your online advertising budget per month.

2. Enter the number of conversions from online advertising that you get per month.

3. Read your current average CPA.

4. Review your potential average CPA with server-side tracking.

5. Check potential savings with server-side tracking.

For eCommerce, use purchase conversions if you want the output to represent cost per purchase. If you mix purchases, add-to-cart events, and leads, the average CPA will not support a clean ROAS or POAS calculation.

The potential CPA is a modeled estimate, not a forecast or guaranteed result. The calculator does not know your margins, average order value, attribution settings, traffic quality, or actual implementation quality. 

The savings result estimates how much less ad spend you would need to produce your current conversion count at the modeled lower CPA.

This is a planning scenario. Tracking setup, consent rates, browser mix, traffic quality, average order value, product margin, and campaign changes influence the results you record after implementation.

For example, you have a monthly ad budget of $10,000 and 300 conversions (completed purchases). The calculator returns these results:

The potential savings compare the current $10,000 spend with the cost of 300 conversions at a $28.74 CPA after switching to server-side tracking. This is why the output shows about $1,379 per month.

In addition to the number of conversions and a CPA, you need two more numbers to estimate ROAS and POAS:

Use these formulas:

In the example from the previous section, the CPA is $33.33 (Ad spend / conversions), and the potential CPA shown by the calculator is $28.74.

Suppose customers spend $100 per order on average:

This means each $1 spent on ads generates $3 in revenue with the current CPA and an estimated $3.48 with the potential CPA.

Now suppose $40 remains from each $100 order after product and order costs:

This means each $1 spent on ads generates $1.20 after product and order costs with the current CPA and an estimated $1.39 with the potential CPA.

Treat the "CPA after switching to server-side tracking" as a starting estimate. To see what changed after the setup, compare the same numbers from before and after the switch.

1. Save your current results. Choose one full period, such as one month. Record your ad spend, purchases, revenue, profit, CPA, ROAS, and POAS.

2. Collect new results after the switch. Use a period of the same length and collect the same data. Do not change your budget, ads, or campaign settings during the comparison. 

Before changing your Google Ads Target ROAS, collect at least four weeks of data. If customers take longer to buy after clicking an ad, wait until those purchases are counted as well.

3. Compare the results. Take CPA and ROAS from your ad platform. Calculate POAS yourself unless your tracking setup already sends profit data to the platform. Compare the before-and-after numbers.

Check whether the new setup records completed purchases that tracking previously missed. Confirm that these purchases are valid and counted once. Recovering missing purchase data gives the ad platform more information to guide its bids, even when your total sales stay the same.

Then compare completed purchases, net revenue, and profit in your business’s sales and accounting records before and after the switch. These figures show whether business results changed. Also check ad spend, discounts, and other changes: a rise in sales alone does not prove that server-side tracking caused it.

ROAS Calculator by Stape uses a planning scenario, while case studies show a range of recorded outcomes.

These are individual company results. They support the value of testing the calculator scenario against your own data, rather than using one percentage as a universal benchmark.

ROAS and POAS answer different questions. ROAS shows how much revenue your ads generate. POAS shows whether enough remains to cover ad spend after product and order costs are paid.

Check both before you decide where to spend more.

Check ROAS and POAS for the same campaign, products, and dates. For example, do not compare ROAS for one month with POAS for one week.

Do not compare ROAS directly with POAS. Compare ROAS with your ROAS target. Then compare POAS with your POAS target.

A target is the minimum result you want the campaign to reach. Targets differ because companies and products have different costs.

If you do not have a ROAS target yet, start with your advertising break-even ROAS. This is the lowest ROAS that covers product, order, and ad costs.

Suppose you have:

The $40 is 40% of your revenue. This percentage is your contribution margin rate:

Now calculate your advertising break-even ROAS:

Why is 250% the break-even point? After product and order costs, only $40 remains from the $100 revenue. The business can spend a maximum of $40 on ads before it starts losing money:

If the business spends the full $40 on ads, nothing remains for fixed business costs or final profit. Its ROAS target therefore needs to be higher than 250%.

For POAS, 100% is the advertising break-even point. It means that the amount left after product and order costs only covers ad spend. Your POAS target needs to be higher than 100% to cover fixed costs and leave final profit.

ROAS tells you whether your ads generate enough revenue. POAS tells you whether those sales leave enough after costs. One result can meet its target while the other misses it, so always check both.

Stape helps you collect the purchase data used for both metrics. Server GTM hosting by Stape runs the server GTM container used to send purchase events to your analytics and ad platforms. Custom Loader helps you capture more complete data, saving it from ad blockers. Stape Analytics shows how many requests were recovered. This all gives you more complete revenue data for ROAS.

POAS Data Feed by Stape helps you track profit. Add the cost or profit margin for each product, and when someone buys a product, the power-up calculates the profit from the order and sends it to your analytics or ad platform. You can then use revenue for ROAS and profit for POAS.

Not sure how good your tracking setup is? Scan your site with Website Tracking Checker by Stape. The free tool finds common issues in web and server-side tracking and gives you steps to fix them.

Revenue, profit, and ad spend must cover the same dates. Include the full conversion delay before you judge the latest period, as some high-margin products have long sales cycles.

Canceled orders, refunds, discounts, and sales tax can make reported revenue larger than the amount the business keeps. Use a documented net revenue value.

Use contribution profit before ad spend in the numerator. Place ad spend in the denominator. If you subtract it from both places, POAS becomes too low and is harder to compare.

Keep one profit definition across products, campaigns, and periods. Document each included cost and update product values when costs change.

An ad platform can report more conversions after tracking improves because it now sees purchases that were missed before. Compare completed orders and revenue in your online store before and after the tracking update. If the store numbers stayed the same, the change shows improved tracking rather than sales growth.

Ad platforms usually receive the full order revenue. They use this value to report ROAS and guide automated bidding. To make bidding focus on profit, the platform also needs a profit value. Keep the revenue conversion for ROAS and create a separate profit conversion for POAS. Test the profit conversion, then choose only one of them to guide bidding, so the same purchase does not influence bidding twice.

In Google Ads, the profit conversion can stay Secondary while you test it. Secondary conversions are normally used for reporting, while Primary conversions guide bidding.