Email Signature Size Guide: Photo, Logo & Banner Dimensions

The number-one reason signatures look amateur isn't the design — it's the images. A 4MB photo blown up to full width, a logo the size of a postage stamp, a banner that overflows on mobile. Here are the exact dimensions that work in Gmail, Outlook, and Apple Mail.

The three golden rules

1. Total signature width: 600px max. Most email clients render around 600px wide. Anything wider gets scaled down unpredictably or clipped — especially in Outlook.
2. Total signature height: under 200px. Taller than that and your signature dominates the message. Aim for 100–150px for a clean one-liner layout.
3. Total image weight: under 100KB. Every image downloads with each email you send. Heavy signatures get flagged by spam filters and annoy recipients on slow connections.

Headshot: 100–150px square

A headshot should be a small square, roughly the height of your text block. Display at 100–150px wide (a circle crop at this size looks sharp and modern). For retina displays, upload a 200–300px source file but set the display width to half — crisp on high-DPI screens without the file bloat of a full-size photo.

• Format: JPG (photos compress far better than PNG)
• Target file size: under 30KB
• Crop tight on the face — shoulders-up, plain background

Logo: 150–300px wide

Logos need to stay legible at small sizes. Display at 150–200px wide (up to 300px for a wide lockup). Keep the aspect ratio — never stretch a logo to fit.

• Format: PNG with transparency — so it sits cleanly on any background
• If your logo has fine text, go wider (250–300px); simple marks can be smaller
• Target file size: under 30KB — run it through a compressor; PNGs with flat colors shrink dramatically

Banner / CTA strip: 600 × 100–150px

A promotional banner ("Book a demo", "New ebook") spans the full signature width: 600px wide × 100–150px tall. This is the one place a wider image is fine — but keep the height restrained or the signature becomes a billboard.

• Format: JPG for photographic banners, PNG for text-heavy graphics
• Keep text large — anything under ~18px equivalent will be unreadable on mobile
• One banner max. Two stacked banners reads as an ad, not a signature.

Social icons: 24–32px

LinkedIn, X, and other icons should be subtle: 24–32px square, in a single row with 8–12px gaps. Use monochrome or brand-color versions — full-color rainbow icon rows date a signature instantly. Target under 5KB per icon.

Formats: what works where

• JPG — photos and banners. Best compression for photographic content.
• PNG — logos and anything needing transparency.
• GIF — only if you actually want animation (see our GIF signature guide). Note: Outlook desktop shows only the first frame.
• WebP — avoid. Smaller files, but Outlook's rendering engine doesn't support it. Your images will break for a large share of recipients.
• SVG — avoid. Almost no email client renders SVG in signatures.

The retina tradeoff, simply

Retina (2x) images look sharper: upload at double the display size, then constrain the display width with the width attribute. A 300px headshot displayed at 150px looks crisp on a MacBook and still weighs very little. Don't go to 3x or 4x — the file-size cost outweighs the visual gain at signature sizes.

Concrete example: your headshot displays at 120px. Export the source at 240px, compress to ~25KB as a JPG, and set width="120" on the image. On a standard screen it looks identical to a 120px file; on a retina screen it's visibly sharper — for about 10KB extra.

Mobile: why signatures look different on phones

Over half your recipients read email on a phone, and this is where oversized signatures fall apart. Most mobile email clients scale the whole message to fit — a 600px signature shrinks proportionally, which is fine. The problems start when images have no explicit dimensions: some clients then render them at native size, so your 2000px logo suddenly fills the screen. Always set width and height attributes on every image. Media queries and responsive CSS are unreliable in email — fixed pixel dimensions are the safe, boring choice that works everywhere.

Five mistakes that scream "amateur"

1. The full-width vacation photo. A 4000px phone photo as a "headshot," displayed at 600px wide. Compress and crop it to 150px.
2. The postage-stamp logo. A 60px logo nobody can read. If the wordmark is illegible below 150px, use the icon-only version of the logo.
3. The 2MB PNG screenshot. Screenshots saved as PNGs are enormous. Re-export as JPG (photos) or re-create as a proper PNG logo file.
4. The WebP "optimization." Smaller file, zero Outlook support. Stick to JPG/PNG.
5. No dimensions set. Images without width/height attributes render unpredictably across clients — always declare them.

Quick reference