Email signature generator › Phone format

Writing a phone number people can actually tap

Most phone numbers in signatures are written for a human reading a business card. Almost everyone reading yours is holding a device that could dial it, if the number were written so it could.

The international format, and why it is not optional

A number written 079 123 45 67 can only be dialled by someone already in that country. From anywhere else it fails, and the reader has to work out the country code themselves — which they will not do.

Write it as +41 79 123 45 67: plus sign, country code, then the national number with the leading zero removed. The plus is the part that matters. It tells any phone in the world to substitute its own international dialling prefix, so the same string works from everywhere.

Auto-detection is fragile

Mail clients scan for things that look like phone numbers and make them tappable. The detection copes well with digits separated by spaces and poorly with dots, slashes and brackets. A number written +41.79.123.45.67 is often not detected at all, and one written +41 (0)79 123 45 67 is sometimes detected and dialled including the zero, which fails.

The parenthesised zero is a print convention meaning "omit this when dialling internationally". A phone does not know that. Drop it.

Write the link yourself

Detection becomes irrelevant if the number is already a link:

<a href="tel:+41791234567">+41 79 123 45 67</a>

The href has no spaces and no punctuation beyond the leading plus; the visible text is formatted for a human. You get correct dialling, and because it is your anchor you can style it rather than accepting the client's blue.

Extensions

An extension after a main number is written in the href with a comma, which most systems interpret as a pause, or with ;ext= which is the formal notation: tel:+41442345678;ext=214. Support varies, and the honest position is that extensions dial reliably nowhere. If you have a direct number, use it instead — it is worth more than any formatting trick.

How many numbers

One. Two numbers make the reader choose, and the most common pair — office and mobile — asks them to guess which you prefer. Pick the one you actually answer.

The exception is where a role genuinely has a switchboard and a direct line and the switchboard is the fallback when you are away. Even then, label them so the choice is obvious rather than presenting two bare numbers.

The check

Send the signature to yourself, open it on a phone, and tap the number. If it dials correctly from a country other than the one it belongs to, it is right. If it is not tappable at all, the detection failed and you need the explicit anchor.

Spacing that helps the reader without breaking detection

Group the digits the way the country groups them — +41 79 123 45 67 in Switzerland, +44 20 7946 0958 in the United Kingdom, +1 415 555 0132 in North America. Plain spaces between groups are detected reliably everywhere and read the way a local expects.

What breaks detection is punctuation: full stops, slashes, hyphens inside the number and brackets around any part of it.

Where the number sits in the block

Directly under the role, above any link. It is the second thing a reader looks for after your name, and putting it below a website address or a legal block means it is found last. At 14 pixels with a line-height of 1.5, the whole name-role-number group occupies about 63 pixels of vertical space, which is the part of the signature that does the work.

Do not label it

"Tel:" or "Mobile:" or a phone glyph in front of the number adds width and tells the reader something they already know from looking at it. The exception is where you list two numbers and the reader has to choose — in which case the label is doing real work, and it is also a reason to consider listing one.

Frequently asked questions