Free tools
Free calculators for A/B tests, conversion rates and ad spend, plus a landing page analyzer
Free calculators from Convertica for the three questions every test raises: what is my conversion rate, how much traffic does a test need, and is the result real? Plus two for paid media, return on ad spend and cost per acquisition, and a landing page analyzer that turns a guided self-check into a fix list. Each calculator shows its formula and a worked example, so you can check the math yourself. No sign-up.
Short answer
Convertica's free CRO tools are calculators for conversion rate, A/B test sample size, statistical significance, ROAS and cost per acquisition, plus a landing page analyzer. Pick one by the question you are asking: where you are now, how much traffic a test needs, whether a result is real, whether your ads pay, or which problems a landing page has.
- Each calculator shows its formula and a worked example, so you can check the math yourself, with no sign-up.
- The three testing calculators follow the order of a fixed-horizon test: measure the baseline, plan the sample, then read the result once.
- Stopping a test at the first good reading raises the chance of a false winner.
- A significant result is evidence, not a guarantee; check revenue as well as the conversion rate.
- The calculators show how to measure and test; they cannot tell you what to change.
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Measure
Conversion rate calculator
Conversion rate from conversions and visitors, or orders and sessions, plus how many conversions a target rate needs.
Answers: What is my conversion rate, and how many conversions would a target rate need?
Use it: Before anything else: to find your baseline, compare two periods or set a goal.
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Plan a test
A/B test sample size calculator
How many visitors each variant needs, and how many days to run, from your baseline rate and the smallest lift worth detecting.
Answers: How many visitors does each variant need, and how many days will the test take?
Use it: Before a test starts, so you know whether your traffic can detect the change you care about.
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Check a result
Statistical significance calculator
A two-proportion z-test for a finished A/B test: the p-value, the lift and a confidence interval for the difference.
Answers: Is the difference between control and variant bigger than chance would explain?
Use it: Once a test reaches its planned sample size, not before.
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Paid media
ROAS calculator
Return on ad spend from ad revenue and ad spend, with ACoS, plus your break-even ROAS from your gross margin.
Answers: How much revenue does each dollar of ad spend bring in, and is that enough to make money?
Use it: When you judge campaigns that report a revenue value, or set a target ROAS.
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Paid media
Cost per acquisition calculator
CPA from cost and conversions, how cost per click and conversion rate make it up, and your break-even CPA.
Answers: What does each sale, lead or sign-up cost, and what is the most I can afford to pay?
Use it: When you judge campaigns by conversions, such as leads or sign-ups, or set a target CPA.
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Check a page
Landing page analyzer
A guided self-check in eight areas, from first impressions to AI agent readiness and SEO fundamentals, with a score out of 100 per area and a fix list.
Answers: Which known conversion problems does my landing page have, and what should I fix first?
Use it: Before you test or redesign a landing page, and after each change.
Which calculator do I need?
Pick the calculator by the question you are asking. To measure where you are now, use the conversion rate calculator. To plan an A/B test before it starts, use the sample size calculator. To read a finished test, or to check whether a change between two periods is real, use the statistical significance calculator. To judge paid campaigns, use the ROAS calculator when conversions carry a revenue value and the cost per acquisition calculator when they are leads or sign-ups. To find which known problems a landing page has before you test it, use the landing page analyzer.
| Your question | Use | You will need |
|---|---|---|
| What is my conversion rate? | Conversion rate calculator | Conversions and visitors (or orders and sessions) for the same dates. |
| How many orders would a higher rate mean? | Conversion rate calculator (second calculator) | Visitors and a target rate |
| Can my traffic support an A/B test? | A/B test sample size calculator | Baseline conversion rate, the smallest lift worth detecting, and daily visitors. |
| How long should my test run? | A/B test sample size calculator | The same inputs plus daily visitors; the result then includes the days needed |
| Did my variant win? | Statistical significance calculator | Visitors and conversions for control and for the variant. |
| Is this month's drop real or noise? | Statistical significance calculator | Visitors and conversions for each period (treat the earlier one as control) |
| Are my ads paying for themselves? | ROAS calculator (with break-even ROAS) | Revenue from ads and ad spend for the same dates; your gross margin for break-even. |
| What does each sale or lead cost? | Cost per acquisition calculator (with break-even CPA) | Total cost and conversions (clicks optional); value per conversion and gross margin for break-even. |
| Which problems does my landing page have? | Landing page analyzer | Your landing page open in another tab, and the yes, partly or no answers. |
| What should I fix or test first? | Free CRO audit | Your website address and email |
How the calculators fit together in a test
The three testing calculators follow the order of a fixed-horizon A/B test: measure the baseline, plan the sample size, run the test to that size, then read the result once. Skipping a step is where most test mistakes start, such as stopping a test early because it looked like a winner.
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Measure your baseline
Use the conversion rate calculator on the page you want to test, over a few normal weeks. That rate is the baseline for the next step.
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Plan the sample before you start
Enter the baseline and the smallest lift worth acting on in the A/B test sample size calculator. If the test would take months, test a bolder change or a busier page instead.
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Run the test to the planned size
Leave it alone until each variant reaches its sample. Checking for significance every day and stopping at the first good reading raises the chance of a false winner.
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Read the result once
Enter the final visitors and conversions in the statistical significance calculator. A significant result is evidence, not a guarantee; check revenue as well as the conversion rate.
The calculators handle the math. The software that collects the data and runs the test is covered in three guides:
- Conversion rate optimization tools: analytics, heatmaps, A/B testing, surveys, user testing, forms, speed and landing pages, sorted by the job each one does.
- A/B testing tools: web testing and product experimentation platforms compared, including free and open source options.
- Heatmap tools: compared by heatmap type and free plan, with how to read a website heatmap.
Free CRO audit
Not sure what to test? Start with the free CRO audit
The calculators tell you how to measure and test. They cannot tell you what to change. Convertica's free CRO audit is an app that reads your page the way a visitor and an AI agent would, and ranks what it finds by likely impact: the first screen, calls to action, forms, trust, mobile, speed, AI agent readiness and SEO fundamentals.
Enter your website and email, and watch the app run live on your page. If you then want help turning it into a test plan, CRO advisory is led personally by founder Kurt Philip.
What the A/B test calculators assume
- Each visitor converts or does not (a yes or no outcome per visitor or session).
- Visitors are split between variants at random and counted the same way.
- The sample is planned before the test and the result read once at the end.
- Two-sided tests by default, with a one-sided option where it is offered.
Each calculator page explains its method in full. Read the conversion rate formula