Posted on 21 July 2026

Email Signature Size & Image Dimensions: The Complete Guide

Get the dimensions wrong and your signature either overflows on mobile or turns your logo into a blurry smudge on retina screens. Get them right and it looks crisp everywhere and loads instantly. Here are the numbers that matter.

Overall signature width

Aim for 300–600px wide. Much wider and it breaks out of the reading pane on phones, forcing horizontal scrolling. A narrower, single-column layout is the safest choice for mobile-heavy audiences.

Logo size

Display your logo at roughly 120–200px wide. Crucially, export the image file at 2× that size (so 240–400px) and then set the display width in the HTML. This keeps it razor-sharp on high-resolution “retina” displays without bloating the layout.

Headshots and icons

• Headshots: around 80–120px square, again exported at 2×.
• Social icons: 16–24px display size; keep them consistent and few.

File size and format

Keep each image well under 100KB — signatures are sent thousands of times, so weight adds up. Use PNG for logos with transparency and JPG for photos. Always set explicit width and height attributes so the layout doesn’t jump while images load.

Why images look blurry — and how to fix it

Blur almost always means the image file is the same size as its display size, so retina screens have to upscale it. Doubling the export resolution fixes it. (We cover this in our documentation on why logos appear fuzzy.)

Never send images as attachments

Attached images show as a paperclip and inflate every email. Host them instead — Mirosign handles hosting for you automatically.

Mirosign’s generator applies correct sizing and retina exports out of the box. Design a sharp, fast signature free →