What is the best width for an email signature?

The ideal width is between 320px and 600px. Keeping it under 400px ensures it looks great on mobile devices.

What is the maximum height for an email signature?

You should aim to keep your signature height under 200px. A tall signature makes email threads look cluttered and hard to follow.

What image quality should I use?

Use standard web quality (72 DPI). If you have a high-resolution screen, 144 DPI is fine, but make sure the file size stays small.

How large should email signature files be?

Try to keep individual images under 50KB. This makes sure your emails load quickly and don't get stuck in spam filters.

Best Email Signature Size Guidelines for 2026

Quick Answer: What is the best size for an email signature?

The best size for an email signature is between 320px and 450px in width and 150px to 200px in height. For high-DPI (Retina) clarity, images should be uploaded at double the display size (e.g., 200px wide for a 100px display) but restricted via HTML width attributes.

Technical Standards: The 'Golden' Dimensions

Component	Standard Size	Why it works
Total Width	320px - 450px	Fits the portrait view of 98% of modern smartphones without overflow.
Total Height	150px - 200px	Prevents "Signature Fatigue" in long back-and-forth threads.
Max File Weight	Under 100KB (Total)	Reduces the risk of the email being marked as 'too heavy' or deferred by filters.

The Retina Problem: Blurry vs. Sharp Logos

Have you ever noticed your logo looks "fuzzy" on an iPhone or a MacBook?

The Cause: High-DPI screens use twice as many pixels to render the same area. A 100px image will look blurry because the screen is trying to fill 200px of physical space.

The Fix: Use the 2x Strategy.

Export your logo at 200px wide.

Set the HTML attribute to width="100".

This packs 200 pixels of data into 100 pixels of space, resulting in crisp, high-definition branding.

Outlook-Specific Sizing Quirks

Microsoft Outlook (desktop versions) is notoriously difficult with sizing because it uses the Word engine for rendering. Our team has observed two critical behaviors:

The DPI Scaling Blowup: If your image doesn't have a 96 DPI metadata flag, Outlook may scale it up by 125% or 150%, making your logo look massive.

Line-Height Expansion: Outlook frequently ignores line-height in pixels. To prevent your signature from looking "stretched," we recommend using mso-line-height-rule: exactly; within your table cell styles.

Mobile Responsiveness: The 450px Limit

Most mobile email clients (Gmail, Apple Mail, Outlook Mobile) reserve about 20-40 pixels for side gutters.

Observation: If your signature is exactly 600px wide, most mobile users will have to scroll 150px to the right to see your social icons.

Behavior-based reasoning: Users rarely scroll horizontally. If your CTA is on the right side of a wide banner, it will be missed.

Pro Tip: Keep your primary contact info in the first 320px of width to ensure it is visible the moment the email is opened.

Image Specifications Checklist

Are my icons 24px x 24px? (Standard for touch targets).

Is my banner width 450px or less?

Did I use the 2x strategy for my headshot?

Is my combined file weight under 102KB? (To avoid Gmail clipping).

FAQ: Email Signature Sizing

Should I use percentages (100%) for width?

No. Many versions of Outlook do not support percentage widths on tables or images. Always use fixed pixel widths (e.g., width="400") for maximum stability.

What is the best format for small icons?

Use PNG-8. It supports transparency and is significantly lighter than PNG-24 or JPEG for small items like LinkedIn or Website icons.

Fix your sizing issues automatically

If you want a signature that is already sized perfectly for every device without you having to touch any code, use the InboxSign generator. It automatically implements the Retina 2x strategy and Outlook-specific spacing fixes.

Best Email Signature Size Guidelines (2026 Guide)