How to Calculate Ad ROI: Formula, Example and the Difference from ROAS

Performance Marketing, 9 min read. By Sefa Aydın. Last updated: September 16, 2026

Plenty of brands see a 5x ROAS in their ad report and still find no money in the till at month end. The reason is simple: ROAS only measures the revenue that corresponds to media spend. It does not see the fee you pay your agency, the videos you shoot, the tools you use or the cost of the product you sell. The only number that tells you whether your ads really pay off is ROI, return on investment.

Below you will find the ROI formula, how it differs from ROAS and how to build a full-cost calculation, using an example in TL. At the end there is a checklist for doing your own calculation and five levers that raise ROI in concrete terms.

What Is ROI? Definition and Formula

ROI is the ratio that shows what percentage of net return the total money you put into advertising produced. It stands for Return on Investment, and the formula is:

ROI = (Revenue - Cost) / Cost

The result is read as a percentage. An ROI of 50% means that every 100 TL you put into advertising brought in an extra 50 TL after covering its cost. An ROI of 0% is the break-even point, and a negative ROI shows that your ads are burning money.

The formula looks simple, but two of its words hide traps. By "revenue", do you mean sales or gross profit? By "cost", do you mean only what you pay Google and Meta, or every cent you spend to keep the ads running? The answers to these two questions produce ROI results ranging from 400% to 5% for the same campaign. The right answer in both cases is the "full" one: gross profit in the numerator, full cost in the denominator.

ROAS vs. ROI: Same Campaign, Two Different Stories

ROAS measures revenue, ROI measures profit. The difference is that clear, but its consequences are huge.

ROAS divides ad revenue by media spend only. If you spent 60,000 TL and made 300,000 TL in sales, your ROAS is 5x. This number is the quick signal a campaign manager needs for daily optimization, and it is the right tool for that job. But it does not answer the business owner's question: did this ad make me money?

ROI answers that question, because it deducts product costs from revenue and adds agency fees and other expenses to spend. The result is a percentage, not a multiplier, and it can drop below zero. In practice, this division of labor works well:

• ROAS for daily and weekly decisions: which campaign, which audience, which creative is more efficient.
• ROI for monthly and quarterly decisions: should the ad budget go up, should you change agencies, should a channel be shut down.

Using one in place of the other is the most common mistake. A brand that makes budget decisions with ROAS grows campaigns that lose money while revenue climbs. Check whether your target ROAS is enough for your profit margin with a break-even ROAS calculation.

Full Cost: What Goes into an ROI Calculation?

For a real ROI, you need to put every item it costs you to run your ads into the denominator. Media spend is only one of them, and for most brands it makes up roughly 60% to 75% of the total. The complete list looks like this:

• Media spend: What you pay Google, Meta, TikTok and other platforms. We explained how this item builds up in our article on Google Ads costs.
• Agency or team fees: The management fee, or the share of an in-house employee's salary that goes to advertising.
• Creative production: Photo shoots, video, design, copy. Spread one-off shoots across the months they are used.
• Tools: Tracking, landing page, email and reporting subscriptions.
• Product and delivery costs: The cost of goods sold, shipping, payment fees, packaging. These do not go into the denominator. They are deducted from revenue to arrive at gross profit.
• Returns and cancellations: Remove returned orders from the revenue attributed to ads.

Skipping any item makes ROI look better than it is and pushes you to invest in the wrong place. Agency fees and creative costs in particular are forgotten in most calculations, even though on small budgets they can reach half of media spend.

Step-by-Step Example: A Month Costing 86,000 TL

A full-cost ROI calculation for an e-commerce brand spending 60,000 TL a month on media is set up as follows. The figures exclude VAT and are net of returns.

Gross profit is what remains after deducting product cost, shipping and payment fees from revenue.

Now let's read the same month with three different methods:

Same month, same campaign. Change the method and the result drops from 400% to 39.5%.

39.5% is still a good result: the ads produced 39.5 TL of net profit for every 100 TL. But if the margin were 30% instead of 40%, gross profit would fall to 90,000 TL and ROI would drop to 4.7%. In other words, the same campaign showing a 5x ROAS would be running just above break-even. You can try your own numbers with the ROAS calculator.

The same calculation for a lead-focused business

For a clinic that generates form fills instead of sales, the calculation has one more step. With 40,000 TL in monthly media and a 12,000 TL agency fee, 180 forms came in and 12% of them turned into appointments, meaning 22 patients. If the average treatment value is 9,000 TL and the gross margin is 55%, revenue is 198,000 TL and gross profit 108,900 TL. Full-cost ROI = (108,900 - 52,000) / 52,000 = 109%.

The trap here is that the ad dashboard only sees the form. The dashboard says "222 TL per form" and tells you nothing about ROI. When the appointment rate drops from 12% to 8%, the number of patients falls to 14, gross profit to 69,300 TL and ROI to 33%, while nothing changes on the dashboard. In a lead-focused business, you cannot build an ROI calculation without CRM data.

Interpreting ROI by Industry

There is no single "good ROI" figure, because industries generate revenue at different times and with different margins.

E-commerce

Revenue is measured instantly, but margins are thin. A full-cost ROI of roughly 20% to 60% is common and considered sustainable. An ROI close to zero can only be justified if you are targeting new customer acquisition and measuring repeat purchases.

Services and lead-focused businesses

Ads produce form fills or calls, not sales. To calculate ROI, you need to know the rate at which forms turn into sales and your average contract value. 200 forms, a 10% conversion rate and an average contract of 25,000 TL means 500,000 TL in revenue. If this data does not come from your CRM, your ROI calculation is only an estimate.

B2B and long sales cycles

The ad cost happens this month, the revenue six months later. Monthly ROI looks negative and misleads you. Use a quarterly or annual window, and set up your measurement using the logic in our article on attribution models.

Whatever your industry, one simple rule works for budget decisions: if a channel's ROI is above your target, increase the budget gradually, because ROI usually falls as you scale. If it is below target, first pull one of the five levers below, then touch the budget. Trying to fix a low ROI by raising the budget only grows the loss.

ROAS tells you how much revenue you made, ROI tells you how much of it stayed in your pocket. Budget decisions are made with the second one.

5 Levers That Raise ROI

There are three things you can change in the ROI formula: increase revenue, increase margin, reduce cost. The five levers touch these three as follows:

1. Conversion rate. More orders from the same traffic grow revenue without adding a single cent to cost. A conversion rate rising from 1.5% to 2% increases revenue by a third. Site speed, product pages and checkout flow are the real work here.
2. Average order value. A free shipping threshold, product bundles and complementary product suggestions raise revenue per order. Revenue grows while ad costs stay flat.
3. Product mix. Shifting ad spend from low-margin to high-margin products raises ROI even if ROAS stays the same. You cannot make this decision without a product-level margin table.
4. Wasted spend. Irrelevant terms in the search terms report, hours of the day that do not convert and saturated audiences usually eat up 10% to 25% of media costs. Cutting them directly shrinks the denominator.
5. Repeat purchases. Sales to existing customers through email and WhatsApp generate revenue at almost zero media cost. Getting a second order from a customer you won through ads doubles that customer's ROI.

Your data tells you which of these levers comes first. If your conversion rate is below the industry average, focus on the site. If product margins are all over the place, focus on the mix. If search terms are polluted, focus on spend. A performance marketing approach that runs all of this together produces far more ROI than tweaking a single campaign setting.

4 Common Mistakes in ROI Calculation

The mistakes that break an ROI calculation are usually not in the formula but in the data that goes into it.

• Crediting the same sale to two platforms. Google and Meta each claim the same order in their own dashboards. If you add up the revenue from both dashboards, revenue looks 20% to 40% higher than it is. Take revenue from your order system, not from the dashboards, and split it across the platforms.
• Revenue including VAT, costs excluding VAT. If conversion values are passed including VAT while costs are recorded excluding VAT, ROI inflates by 20% on its own. Bring both onto the same basis.
• Using revenue instead of gross profit. In the example above, the entire gap between 400% and 39.5% came from this mistake. An ROI calculated without deducting product cost is not ROI.
• Booking a one-off expense in a single month. If you book a 60,000 TL shoot in the month it happened, ROI collapses that month and the next six months look better than they are. Spread creative spend across the months it is used.

Fixing these four mistakes removes, in most accounts, the optimism that makes ROI look better than it is, but in return it gives you a reliable decision metric for the first time.

Implementation Checklist

To set up your own ROI calculation this month, do the following in order:

• Pull the last 3 months of media spend by platform.
• Add agency fees, creative and tool costs, split into monthly shares.
• Net the revenue attributed to ads after returns and cancellations, excluding VAT.
• Calculate gross margin per product. Do not use a single average.
• Apply the formula ROI = (gross profit - total cost) / total cost.
• Break the result down by channel and question the budget of the channel with the lowest ROI.
• Repeat the calculation every month with the same method so the comparison is meaningful.

Once an ROI calculation is in place, the debates about advertising end. Which channel to grow, which agency to keep and when to raise the budget are read from the number itself. If you want to work out the real return on your ad investment together, contact us for a free consultation.

Related articles

• What ROAS is and how to increase it
• What break-even ROAS is
• Google Ads costs
• E-commerce unit economics: CAC, LTV and contribution margin

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