Email image sizes
There is no standards body for email image dimensions. No W3C spec, no platform requirement, nothing equivalent to the numbers Meta or Etsy publish. Every figure you will find for an email header or banner is convention — widely followed, but convention.
The convention that matters is the body width. 600 pixels became the default because it fits Outlook's narrow reading pane without horizontal scrolling and scales down cleanly on a phone, and it stuck. Mailchimp's legacy templates are 600px and its current builder is 660px, which is the closest thing to a citable anchor. Everything else on this page — header heights, banner heights, signature proportions — is design convention built on top of that width, and is labelled as such.
Quick reference
| Format | Dimensions | Ratio | Max size |
|---|---|---|---|
| Email Header | 600 × 200 px | 3:1 | — |
| Email Banner | 600 × 300 px | 2:1 | — |
| Email Signature | 600 × 150 px | 4:1 | — |
Email Header600×200px
Email headers are built to a 600 pixel body width. A header of 600×200 is the common convention, though the height is a design decision rather than a specification. The width is the part that matters: 600px fits Outlook's reading pane and scales cleanly to mobile, and it is what most email service providers ship as their default template width.
The honest answer to "what size should an email header be" is that nobody specifies it. Email has no owning platform, so there is no equivalent of Meta's ads guide or Etsy's help centre to cite. What exists is a convention: a 600 pixel body width, with header artwork built to fill it.
Dimensions
600×200
Aspect ratio
3:1
Formats
JPG, PNG, GIF
Also supports
Best practices
- •Build to 600px wide. It is a convention, but it is the one nearly every client and template assumes.
- •Supply at 1200px wide and constrain with CSS so the header stays sharp on retina screens.
- •Height is your choice — 150–200px is typical for a masthead. Nothing enforces it.
Email Signature600×150px
Email signatures are typically built no wider than the 600 pixel email body, with 600×150 a common footprint and logos around 150–300 pixels wide. Like every email dimension this is convention, not specification — and signatures carry one extra rule that matters more than any number: do not build the whole signature as a single image.
The dimension question for signatures is less important than the format question. A signature built as one flat image looks perfect when it renders and disappears entirely when the client blocks images — which, for a signature, means the recipient sees nothing where your name, title and contact details should be. Build the signature as HTML text with a small logo image, not as a single graphic.
Dimensions
600×150
Aspect ratio
4:1
Formats
JPG, PNG, GIF
Also supports
Best practices
- •Build signatures as HTML text with a small logo image — never as one flat graphic.
- •Keep the logo to 150–300px wide, supplied at double for retina.
- •Keep the file small; signatures are re-quoted through every reply in a thread.
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Start designing →Frequently asked questions
What is the standard email width?
600 pixels is the long-standing convention, and Mailchimp's legacy templates use it. Mailchimp's newer builder is 660px. There is no official standard — no standards body specifies an email width.
Why is 600px the email standard?
It fits Outlook's narrow reading pane without horizontal scrolling and scales down cleanly to phone widths. It is a convention that survived because it works, not a rule anyone published.
What size should email images be for retina screens?
Mailchimp recommends supplying images at 600–1200px for its legacy 600px templates and 660–1320px for the newer 660px builder — roughly double the display width, then constrained by CSS.
Is there an official email image size specification?
No. Unlike social platforms, email has no owner and therefore no spec. The dimensions on this page are conventions anchored to the widths email service providers actually ship in their templates.
Other platform guides
Guide last verified: August 28, 2026. This hub summarizes 3 formats and cites 2 sources across this page and the linked format pages.
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