A/B Test: What Magic Number of Opt-in Form Fields Caused a 120% Conversion Increase?


Even when I’m hungry, I can still manage to think about A/B testing.

Case in point: last Friday, some colleagues and I ventured out to a food truck for lunch. I was about to order a Philly cheesesteak when our intern Blake pointed out another option. It was called the Gunnar, and it was the same thing—with twice as much meat.

Since I was famished, I decided to indulge and get this epic sandwich. But while I was waiting for my order, I wondered:

Had I made the right choice? Did I ask for too much?

It occurred to me that marketers ask themselves this question all the time—whenever we’re deciding how much information to ask our leads for, actually. A LeadBox™ with multiple form fields might be too much for some visitors to chew on. But if they’re hungry enough for what you’re offering, it might be just right.

In our test today, Tom Challan used two LeadBox™ variants to give away his lead magnet, How to Crush Your Fear of the Phone. One had just one form field, while the other had three.

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2 And the Winner Is...
3 Form Fields
1 Form Field
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2 And the Winner Is...
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YES! Nice call!
Nope! Try Again Next Time!
Winner: Version A created an overall increase of 120.39%
20% 80%

How People Voted

Click here to see our take on these results

If you chose Version A you are correct!

Version A, with a 100% probability of outperforming Version B, increased opt-ins by 120.39%.

Although we can’t say with total certainty why this change caused the increase, here are a couple of my speculations:

  1. The use of 3 form fields increased the perceived value of the book, thus increasing opt-ins.
  2. People are often reluctant to provide their phone number online, but in this case the lead magnet is actually about overcoming your fear of the phone. This may have prompted visitors to overcome any reluctance they may have normally felt.

While asking for visitors to complete fewer form fields is typically the industry best practice, keep in mind that your own audience may differ. To find out how many form fields you should feature in your own LeadBoxes®, run an A/B test!

Why do you think Version A outperformed Version B? Let us know in the comments!

Click here to get the free split-test guide

What Do You Think?

Did this test’s results surprise you? Why do you think Version A increased conversions so dramatically? Leave a comment below and let us know your thoughts.

If you’re new to LeadPages, you should know that all Pro and Advanced users can run any A/B test inside LeadPages in just five clicks.

Do you have a LeadBox™ like this one that you would like to test? If so, you can set up the exact same type of test in under a minute. You can also A/B test headlines, text colors, images, calls to action, and just about any other change you can think of.

Watch the quick video below for an introduction to enabling split testing on your LeadPages account.


  • Wrong again !

    • John Nye

      Don’t worry Keely! This is a very difficult topic. Not too long ago we covered a split test where a LeadBox with 2 form fields competed against 1 form field. In that test, the LeadBox with the single form field won. The results vary by business for the most part and that’s why split testing is a great tool to find out what works best for your business. 🙂

      • I nearly went for A due to the phone field relating to the giveaway, but decided one field was easier! Tricky one – and these A/B posts are gold for your marketing 😉

        • John Nye

          Thanks Keely! These posts are certainly great for marketing, no doubt. But ultimately, we want to provide our readers with real-life split test cases to show them that just because a strategy is an industry-best practice, it doesn’t mean that it will be the best for your business. That’s where split testing comes in to save the day! 🙂

  • I always guess the wrong ones! It’s irritating. LOL Just when I think I’m learning really well and was sure. Now I’m irritated AND confused. 🙂 Hahaha!!!

    • John Nye

      Do not fear Kelly! This is a very tricky test topic. This one even caught me off guard!