There is no official standard for how big an email signature should be, which is why so many of them break on a phone or get clipped by Gmail.
These are the working numbers — width, height, file size and total weight — that keep a signature readable in every major client.
Aim for a total width of 300 to 600 pixels, and treat 650 as a hard ceiling. Beyond that, mobile clients either shrink the whole thing or force horizontal scrolling, and neither looks professional.
Height should stay under about 200 pixels. A signature taller than the reply it is attached to reads as clutter, and on a long thread it repeats endlessly.
Display size of 100 to 300 pixels wide, typically 50 to 100 tall. Export at twice those numbers so it stays sharp on high-density screens — see our guide to blurry logos.
Use PNG for transparency and clean edges. Keep the file under 50 KB.
Square, between 80 and 150 pixels on each side. Anything smaller becomes an unrecognisable thumbnail; anything larger dominates the signature.
Crop tightly to the head and shoulders — a full-body shot at 100 pixels shows nothing useful. Export at 2x, keep under 60 KB.
The most commonly oversized element. Match the width of your signature block, typically 500 to 650 pixels, at a height of 70 to 150.
A banner taller than 150 pixels dominates the message and gets read as an advertisement rather than as part of your identity. Keep the file under 100 KB and put one message on it, not three.
Between 16 and 32 pixels, with 24 as a sensible default. Export at 2x, because small images are where softness shows most.
Four to six icons is the practical maximum. Beyond that they become visual noise and each one gets less attention than it would have on its own.
Two thresholds matter in practice.
The 102 KB Gmail clip. Gmail truncates any message above roughly 102 KB and hides the remainder behind a “view entire message” link. On a long reply chain where your signature repeats on every message, a heavy signature is often what pushes a thread over the line — and your signature is at the bottom, so it is the first thing hidden.
The 10,000-character Gmail signature limit. Separate from the above, and covered in detail in our guide to the Gmail signature character limit.
Keep the signature HTML itself under about 10 KB and the combined weight of all images under 500 KB.
More than half of business email is now opened on a phone, and a phone viewport is around 320 to 375 logical pixels wide.
Practical implications:
| Element | Display size | Export at | Max file size |
|---|---|---|---|
| Whole signature | 300–600 px wide | — | 500 KB total |
| Logo | 100–300 px wide | 2x | 50 KB |
| Profile photo | 80–150 px square | 2x | 60 KB |
| Banner | 500–650 × 70–150 px | 2x | 100 KB |
| Social icon | 16–32 px | 2x | 5 KB each |
| Signature HTML | — | — | 10 KB |
Templates in the Mail Ink generator are already built to these proportions, with images processed to the right dimensions and compressed on upload — so you get a signature that fits without measuring anything.