We’re all about easy—this running list is designed to be your go-to cheat sheet for the latest email designs by the numbers. Bookmark this page as you plan out your next email campaigns.


What’s the Best Width for an Email?

If you want a safe bet, shoot for 600 pixels. 600 pixels is the standard width for email, and while there are exceptions (including options that allow for up to 960 pixels), 600px will keep you well within the bounds of the majority of inboxes. If you want to experiment, give yourself a max width of 960px and be sure to run an inbox preview.


What’s the Best Height for an Email?

You’ve heard of keeping things “above the fold”? This term used to refer to keeping the best stuff above the “fold” of a newspaper. In digital marketing, the term has been co-opted for inboxes and webpages, and anything below the fold gets into the land of “to scroll or not to scroll.”


So what does that mean for email height? If you have a reason to scroll, scroll—recipients are accustomed to scrolling for content, and depending on your images, the inbox, and the open experience, where the fold lands could change. As a good practice, however, do keep your primary message (your reason for sending) and a relevant call to action as close to the top as possible—within 300px is ideal.


How Much Text Fits in the Preheader?

The amount of preheader text displayed depends on device, inbox, and settings. As a general rule, get the important stuff in the first 35 characters. If you know where the bulk of your opens happen, Gmail typically displays between 100 and 110 characters, and iPhones typically display 35 characters—just be sure to run an inbox preview to see what you’re working with. There have been notable email fails when preheader text gets cut off in unforeseen places!


How Long Should a Subject Line Be?

ReturnPath recommends 65 characters, and most are between 40 and 50 characters. Recent evidence doesn’t show a correlation between subject line length and open rates, but there are a few things you should keep in mind:

  • Overuse of all caps, too much punctuation, and some words can land you in the spam filter
  • Emojis should be used with caution—and A/B tested for performance
  • Personalized variables can help open rates by as much as 26%, if you don’t overuse them


What’s a Good Guide for Total Email Size?

This is the estimated HTML size (not including images). We recommend keeping this under 100KB to avoid deliverability issues.


What Are the Best Font Sizes?

As a general rule—and taking mobile into consideration—target:

Headlines: 30px minimum

Body Copy: 16px minimum

Smallest Text: 13px minimum


What’s a Good Guide for Button Size?

You can’t go wrong with a button the size of the average thumb—which is to say, 44 x 44 pixels. But, since it’s uncommon to see a true square in an email, just avoid anything smaller than 44px in height or width. Don’t forget to give those buttons some room—shoot for a CTA text padding of 20px, at a minimum.


What’s a Good Size for a Header Image?

Your top 300 pixels are precious—don’t waste them, as this is what most recipients see first. This requires some testing, but for general best practices, go for 600px wide and no more than 250px high (and save some room for that headline).


How Much Marketing Content Can Be Included in a Transactional Email?

You can include a small amount of marketing content in a transactional email but be careful—as a general rule of thumb, shoot for 75% transactional content and no more than 25% marketing content.


Didn’t see what you were looking for? Ask us in the comments below or email us at expert@emfluence.com and we’ll update this post.


  1. LOVE this! I’m always getting asked for these numbers from designers. Definitely bookmarking this (and telling my designers to bookmark it!)

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