Call To Action Buttons: Does Size Matter?

I came across a website (that will remain nameless) while searching for a good tasting Swiss-water decaf coffee. (Does one exist? Please advise in the comments!) I noticed on the product page that it had perhaps the world's tiniest Buy button.

They Say Bigger Is Better

Many conversion optimization cheerleaders who suggest larger buttons convert better, and some tests show even different colors can perform better. Marketing Sherpa credits cart button design as one of 7 tweaks that helped Newegg.com boost online sales by 30%.

#7. Bigger, flashier cart button

"It used to be just a cart with a little arrow. It wasn't big enough. People's eyes weren't going there, so we made it big, bold and very exciting to look at," said Stuart (Wallock, Marketing Director of NewEgg.com). The team a/b tested several different cart icons before picking the winner, so go check it out.

This is the evolution of NewEgg's cart icon design:

Wallock mentions several different cart buttons were A/B tested in the last redesign - we're not sure if they were different colors and different sizes, but the "winning" icon is not a relatively large button compared to other retailers':

(From our collection of shopping cart buttons)

Testing Different Designs

Back to our decaf coffee product page. I mocked up some alternative pages which hypothetically could be used in split testing.

Here the buttons are bigger - easier to read. But the Continue Shopping button is larger than the Add to Cart. Probably not the best design.

Here's an alternate version with the button text "Buy." This would make a good split test to determine which button text converts higher (with the same button design).

Personally I prefer a design like this - a large, easy to read and well-positioned Buy or Add to Cart button, with a less prominent text link back to shopping.

But maybe the white button doesn't stand out enough? We'll throw in a sweet jelly bean red button, because some swear that red "stands out more." Check out a couple lively discussions from people who have actually tested this at Grokdotcom here and here.

Split-Testing Resources

Google Website Optimizer makes it easy for anyone with an AdWords account to run simple split tests. GrokDotCom has compiled Google Website Optimizer - 7 Free Resources To Get Started including a downloadable guide and white paper, podcast and webinar archive on the subject of A/B split testing with Google Website Optimizer. They even developed a WordPress Plug-In for it.

Google also has its own training video here.

This post was originally published in February 2008 and was selected as part of our current "Best Of" series.