Email signature generator › Sizing
Email signature size guide
There is no standard, but there are limits imposed by preview panes, phone screens and blocked images. These numbers work across all three.
Your details
Layout
Logo or photo — optional
Drop an image here or click to choose
PNG or JPG, under 2 MB
or use a hosted image
Preview
Nothing is uploaded and nothing is stored. The image you drop stays in this browser.
Overall dimensions
| Dimension | Recommended | Reason |
|---|---|---|
| Width | Under 600 px | Reading panes are narrow; wider forces horizontal scrolling on phones |
| Height | Under 150 px | Taller and the signature dominates a short message |
| Lines of text | 3–5 | Beyond five, people stop reading any of it |
| Total HTML | Under 5 KB | Gmail caps at 10,000 characters and clips long messages |
Font sizes
Email is read on phones more often than desktops, and anything under 12 px is genuinely hard to read there. iOS also auto-enlarges text it considers too small, which breaks carefully aligned layouts.
- Name: 15–17 px, bold. The only element that needs weight.
- Role and company: 13–14 px, grey.
- Contact details: 12–13 px.
- Disclaimer, if you must: 10–11 px, light grey.
- Never below 10 px.
Set sizes in px, not pt, em or rem.
Relative units resolve against a base that varies by client, and pt is
converted inconsistently.
Logo and photo
- Square logo or photo: 64–100 px displayed, file exported at 2×
- Wide logo: up to 200 px wide, 60 px tall
- File weight: under 50 KB; under 20 KB is achievable for most marks
- Always set
widthandheightattributes — without them Outlook may render the image at its native pixel size, which is how a logo suddenly appears 500 px wide
Line height and spacing
Use line-height:1.5 to 1.6 on multi-line blocks. Tighter looks
cramped at small sizes; looser makes the signature taller than the message. Space blocks with
padding-top of 8–12 px on the cell, not with empty <br> tags —
clients collapse or duplicate stray line breaks unpredictably.
The mobile check that matters
Send the signature to yourself and open it on a phone. Three things to look for:
- Does anything require horizontal scrolling? Then it is too wide.
- Does the logo push text off the edge? Then the side-by-side layout needs to become stacked.
- Is any text uncomfortable to read at arm's length? Then it is too small, regardless of what the desktop preview suggested.
Then repeat with images disabled. What remains should still be a usable signature — that is the real test of whether you have put information inside a picture.
Where the space actually goes
People assume a signature is too tall because of the text. It almost never is. Measured on a typical five-line signature, the height comes from:
| Element | Typical height |
|---|---|
| Logo at 100 px | 100 px — two thirds of the total on its own |
| Five lines of 13 px text at line-height 1.6 | about 104 px |
| Padding between blocks | 20–30 px |
| A call-to-action button | 34 px plus its padding |
| A three-line disclaimer at 10 px | about 48 px |
Which gives the practical order for cutting: shrink the logo to 64 px, then drop the disclaimer if it is not required, then remove a contact line. Reducing the font sizes is the worst option — it saves the least height and costs the most readability.
Testing without a testing service
Paid tools render a signature across dozens of clients, but for a signature that is overkill. Three accounts cover the overwhelming majority of what your recipients use:
- Gmail in a browser — the widest desktop audience.
- Outlook for Windows, if you can reach one. It is the strictest renderer, so a signature that survives Outlook survives nearly everything. Outlook on the web is not a substitute: it uses a browser engine and will happily render CSS that the desktop client ignores.
- Any phone — for width and legibility.
Send the same test message to all three, then look at it once with images blocked. Four checks, ten minutes, once.
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Frequently asked questions
What is the ideal email signature size?
Under 600 pixels wide and under 150 pixels tall, with three to five lines of text and the whole HTML under about 5 KB.
What font size should an email signature use?
15 to 17 px for the name, 13 to 14 px for role and company, 12 to 13 px for contact details. Never below 10 px, and always in px rather than pt or em.
How large should the logo in an email signature be?
64 to 100 pixels for a square mark, up to 200 by 60 for a wide one, exported at twice the display size and kept under 50 KB.
Why does my signature logo appear enormous in Outlook?
Because the img tag has no explicit width and height attributes, so Outlook falls back to the image's native pixel dimensions.
Should email signature font sizes use px or em?
px. Relative units resolve against a base font size that varies between mail clients, so an em-based signature renders at different sizes for different recipients.