How to Calculate Your Google Ads ROI: An Interactive App (and the formulas behind it)
If you’re running Google Ads or thinking about it, you’ve probably asked the same question every business owner asks:
“Is this actually going to make me money?”
It’s a fair question. And too often, the answer is buried in spreadsheets, jargon, and guesswork.
That’s why we built an interactive Google Ads ROI Calculator that lets you compare two campaign scenarios side by side and see exactly how each variable impacts your bottom line, in real time.
In this post, I’ll walk you through every input, every output, and every formula so you understand not just what the numbers say, but why they matter.
Key Takeaways:
This document introduces an interactive Google Ads ROI Calculator that compares two campaign scenarios using six inputs (Impressions, CTR, Enquiry Rate, CPC, Sales Conversion Rate, and ATV) to calculate eight financial outputs, including ROAS. Key findings suggest that prioritizing improvements to the Enquiry Rate and Sales Conversion Rate offers the highest-leverage ROI gains, and a healthy ROAS target is typically 300-500%+.
Table of Contents
The Calculator: What It Does
Our ROI Calculator takes six adjustable inputs, the things you can control or influence in a Google Ads campaign, and calculates eight outputs that show you the financial impact of those inputs. There is an option at the top of the calculator to select whether you’re doing this for a lead generation business or for an e-commerce one, and it will change the inputs and the outputs accordingly.
You set up two scenarios (Scenario A and Scenario B), adjust any of the inputs, and instantly see how the results compare. It’s designed to answer questions like:
- What happens to my revenue if I improve my landing page conversion rate by 3%?
- How much more would I earn if I increased my ad budget to get more impressions?
- Is it worth paying a higher cost per click for a more competitive keyword?
The 6 Variable Inputs (What You Control)
These are the levers you can pull. Each one represents a factor in your Google Ads campaign that you can adjust, optimise, or influence.
1. Impressions
What it is: The number of times your ad is shown to people on Google in a given month.
Why it matters: Impressions are the top of your funnel. No impressions means no clicks, no enquiries, and no sales. Your impression volume is largely driven by your budget, keyword targeting, and how competitive your market is.
Typical range: This varies wildly by industry. A local plumber might see 2,000-10,000 impressions per month. A national e-commerce store could see 500,000+. To get an idea, go to the Google Keyword Planner (yes, do an old fashiond Google search for this) and check on one or some of the keywords to see how many searches there might be on an average month. You can multiply it by a few times because it’s probably not showing you everything and all the organic searches.
2. Click-Through Rate (CTR)
What it is: The percentage of people who see your ad and actually click on it.
Why it matters: CTR is a direct measure of how compelling your ad copy and offer are. A higher CTR means more people are interested enough to visit your website. It also affects your Quality Score in Google Ads, which can lower your cost per click.
Typical range: Average CTR across industries is around 3-5% on the search network. Well-optimised campaigns can achieve 7-10%+. It also depends on what sort of channel. For example, shopping ads will obviously command a lower click-through rate, as do display ads, compared to search ads, which can often be much higher. So if you’re already running Google Ads, you’ll have a fair idea of where that’s sitting.
Formula: CTR = (Clicks ÷ Impressions) × 100
3. Enquiry Rate (Conversion Rate)
What it is: The percentage of people who click your ad and then take a desired action on your website, typically filling in a contact form, calling you, or requesting a quote. In e-commerce, this would we’ll be actually checking out and buying one of your products, which would have a dollar value attached to it if it’s set up correctly.
Why it matters: This is where your landing page does the heavy lifting. You can drive all the traffic in the world, but if your website doesn’t convert visitors into enquiries, you’re leaving money on the table. This is often the single biggest lever for improving ROI.
Typical range: 2-5% is average for many industries. Strong landing pages or more urgent types of services can achieve 10-15%+.
4. Cost Per Click (CPC)
What it is: The average amount you pay each time someone clicks on your ad.
Why it matters: CPC directly determines your total ad spend. It’s influenced by your industry, keyword competition, Quality Score, and bidding strategy. Lower CPC means more clicks for the same budget, but sometimes paying more per click for higher-intent keywords delivers better overall ROI.
Typical range: $1-$5 for many industries. Highly competitive sectors like law, finance, and insurance can see $15-$50+ per click. And obviously rates will vary from country to country.
5. Sales Conversion Rate
What it is: The percentage of enquiries that turn into actual paying customers.
Why it matters: This is your sales team’s domain (or your checkout process for e-commerce). Getting enquiries is only half the battle, you need to close them. This variable bridges the gap between marketing performance and actual business revenue.
Typical range: 10-30% for service businesses. E-commerce checkout completion rates vary from 1-5% of total visitors but can be much higher as a percentage of people who initiate checkout.
6. Average Transaction Value (ATV)
What it is: The average revenue you earn from each new customer or sale.
Why it matters: ATV determines how much each conversion is actually worth to your business. A business with a $5,000 ATV can afford a much higher cost per acquisition than one with a $50 ATV and still be wildly profitable.
Typical range: Depends entirely on your business. A café might average $15 per transaction. A law firm could average 20 to 30 thousand, but sometimes much higher, depending on the area of law. A renovation company might average $50,000. For e-commerce businesses, it will depend on the product. ATV could be $100 or it could be thousands of dollars.
The 8 Calculated Outputs (What the Numbers Tell You)
These metrics are all calculated automatically based on your six inputs. Here’s what each one means and how it’s calculated.
1. Clicks
What it is: The total number of people who click on your ad in a month.
Formula: Clicks = Impressions × (CTR ÷ 100)
Example: 10,000 impressions × 5% CTR = 500 clicks
2. Total Ad Cost
What it is: Your total monthly Google Ads spend.
Formula: Total Ad Cost = Clicks × Cost Per Click
Example: 500 clicks × $5.50 CPC = $2,750.00
3. Number of Enquiries
What it is: The total number of leads or enquiries generated from your ad traffic.
Formula: Enquiries = Clicks × (Enquiry Rate ÷ 100)
Example: 500 clicks × 10% enquiry rate = 50 enquiries
4. Cost Per Lead (CPL)
What it is: How much you’re paying, on average, for each enquiry or lead.
Formula: Cost Per Lead = Total Ad Cost ÷ Number of Enquiries
Example: $2,750 ÷ 50 enquiries = $55.00 per lead
Why it matters: CPL tells you how efficient your advertising is at generating interest. If your CPL is too high relative to your average transaction value, you may need to optimise your landing page, ad copy, or targeting.
5. Total New Business Conversions
What it is: The number of enquiries that actually convert into paying customers.
Formula: New Business Conversions = Number of Enquiries × (Sales Conversion Rate ÷ 100)
Example: 50 enquiries × 30% close rate = 15 new customers
6. Cost Per Acquisition (CPA)
What it is: How much you’re spending in ad costs to acquire each new paying customer.
Formula: CPA = Total Ad Cost ÷ Total New Business Conversions
Example: $2,750 ÷ 15 customers = $183.33 per acquisition
Why it matters: CPA is one of the most important metrics for any business running ads. Compare this to your average transaction value, if your CPA is lower than your ATV, you’re profitable on the first transaction. If your customer also has a high lifetime value (repeat purchases, ongoing services), even a higher CPA can be worthwhile.
7. Total Revenue
What it is: The total revenue generated from your new customers.
Formula: Total Revenue = Total New Business Conversions × Average Transaction Value
Example: 15 customers × $500 ATV = $7,500.00
8. Return on Ad Spend (ROAS)
What it is: The total revenue generated as a percentage of your total ad spend. This is the headline metric, it tells you whether your advertising is making or losing money.
Formula: ROAS = (Total Revenue ÷ Total Ad Cost) × 100
Example: ($7,500 ÷ $2,750) × 100 = 272.7%
What the number means:
- ROAS above 100% = You’re earning more than you spend. A 272.7% ROAS means for every $1 you spend on ads, you get back $2.73 in revenue.
- ROAS of exactly 100% = You’re breaking even (revenue equals ad spend, but you’re not accounting for your other costs).
- ROAS below 100% = You’re spending more on ads than you’re earning back.
A healthy ROAS target for most businesses is 300-500%+, but this depends heavily on your margins. A business with 80% gross margins can be profitable at a lower ROAS than one with 20% margins.
How to Use the Calculator Effectively
Here are a few practical ways to get the most out of this tool:
1. Model your current performance first.
Plug your real numbers into Scenario A. If you’re already running Google Ads, pull your actual impressions, CTR, CPC, and conversion rate from your Google Ads dashboard. This gives you an honest baseline.
2. Test one variable at a time.
Change just one input in Scenario B, for example, increase your enquiry rate from 5% to 8%. This isolates the impact of that single improvement so you can see exactly what it’s worth.
3. Prioritise the highest-leverage changes.
In most campaigns, improving your enquiry rate (landing page conversion) or sales conversion rate delivers the biggest ROI improvement without spending an extra cent on ads. Start there before increasing your ad budget.
4. Use it in client conversations.
If you’re an agency, consultant, or service provider, this calculator is a powerful tool for demonstrating value to prospects. Show them Scenario A (their current situation) vs. Scenario B (what’s possible with your help).
This Isn’t Just for Google Ads
The underlying logic of this calculator, inputs, conversion rates, and revenue outcomes, applies far beyond Google Ads. The same framework works for any business that wants to model the financial impact of changes to their marketing, sales, or pricing.
Digital marketing agencies can use it to show prospective clients the ROI of improved campaign management.
Financial advisors could build a version that models investment returns across different portfolio scenarios.
Health and wellness consultants could quantify the cost of inaction vs. the value of engaging their services.
SaaS companies could visualise the revenue impact of improving their trial-to-paid conversion rate.
The principle is the same: take the inputs you can influence, calculate the outputs that matter, and let the numbers tell the story.
Try It Yourself
We’ve made the calculator freely available. Play with the sliders, type in your own numbers, and see what’s possible for your business.
Try the Google Ads ROI Calculator
And if you’d like help turning those Scenario B numbers into reality, we’d love to chat.
