A/B Test Significance & Sample Size Calculator
Two calculators in one: find out whether the difference between your variants is statistically significant, and work out how many visitors each variant needs before you launch the test.
How to use the A/B Test Calculator
- Before the test: enter your current conversion rate and the smallest lift worth detecting to get the sample size.
- Run the test until each variant reaches that sample size — don’t stop early because one side looks ahead.
- After the test: enter visitors and conversions for both variants to see whether the result is significant.
- Significance check Two-proportion z-test with conversion rates, relative lift and p-value.
- Sample size planner Visitors needed per variant for your baseline rate and the smallest lift you care about.
- Plain-English verdict Tells you what the numbers mean, not just the numbers.
- Private by design All maths runs in your browser. Nothing is sent to us.
Tactics this tool helps with
- Acquisition
Capture emails and SMS sign-ups with a first-order welcome offer
Offer new visitors a first-order discount or perk in a well-timed pop-up, collect email then SMS with consent, and deliver the code by message.
Impact High Effort Low + free toolCategories: Conversion, Email - Acquisition
Let qualified visitors book a demo instantly from your form
Show a calendar right after the demo form so qualified leads pick a time with the right rep in one step, instead of waiting for an email back.
Impact High Effort Low + free toolCategories: Conversion, Sales - Acquisition
App store optimisation for the App Store and Google Play
Tune your app's name, keywords, screenshots and ratings so more people find it in store search and tap install.
Impact High Effort Medium + free toolCategories: SEO, Conversion, A/B Testing - Acquisition
Build a product-finder quiz that segments and converts shoppers
Ask shoppers a few quick questions, recommend the right product with a clear reason, and use their answers to personalise follow-up emails.
Impact High Effort Medium + free toolCategories: Conversion, Email, Customer Research - Acquisition
Decide your A/B test sample size before you start
Work out how much traffic a test needs up front, then judge it once, so you stop shipping winners that were never real.
Impact High Effort Medium + free toolCategories: A/B Testing, Analytics - Acquisition
Build a creative testing system for Meta and TikTok ads
Test ad concepts in a structured weekly cycle, judge them on cost per purchase or install, and move winners into scaling campaigns.
Impact High Effort High + free toolCategories: Paid Ads, A/B Testing - Acquisition
Catch leaving visitors with a useful exit offer
Show a single, genuinely helpful offer when visitors are about to leave a key page, and run it as a proper test to prove it adds conversions.
Impact Medium Effort Low + free toolCategories: Conversion, A/B Testing - Activation
How to reduce checkout abandonment with a simpler checkout
Cut fields, allow guest checkout, add express wallets and show every cost early so more shoppers who reach checkout actually pay.
Impact High Effort Medium + free toolCategories: Conversion, A/B Testing - Activation
Reduce signup friction with fewer fields and social login
Cut signup to the minimum, offer one-tap login options and let people try the product before creating an account, so more visitors become users.
Impact High Effort Medium + free toolCategories: Conversion, Onboarding - Activation
Test your free trial length instead of guessing
Run a controlled test of different trial lengths, including a reverse trial, and pick the one that produces the most paying customers.
Impact High Effort Medium + free toolCategories: Pricing, A/B Testing - Revenue
Build three pricing tiers that point to the middle
Design good, better and best plans so the middle tier looks like the obvious choice for most buyers.
Impact High Effort Medium + free toolCategories: Pricing, Conversion - Revenue
Show upgrade prompts when users hit a limit
Put a clear, helpful upgrade offer in front of users at the exact moment their plan stops them from doing something.
Impact High Effort Medium + free toolCategories: Pricing, Conversion, Onboarding
Frequently asked questions
What does statistically significant mean here?
At 95% confidence, a significant result means a difference this large would be unlikely (under 5% chance) if the two variants actually performed the same. It does not tell you the exact size of the real effect.
Why can’t I stop the test as soon as it is significant?
Checking repeatedly and stopping at the first significant moment inflates false positives well above your chosen error rate. Decide the sample size up front and evaluate once you reach it.
What is minimum detectable effect?
The smallest relative improvement you want the test to be able to detect. Smaller effects need far more traffic — halving the effect roughly quadruples the sample size.
Want this handled for you?
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