Make a phone number QR code

How a phone handles a call code

The code holds a tel: link, the standard way to describe a number to dial. A phone that scans it shows the number and offers to call it. On current iPhones and Android phones, the person has to confirm or press the call button, so a scan alone does not start a call.

Tablets and laptops that cannot place calls may offer another calling app, or do nothing. If people might scan the code from one, add the number in words next to it.

Calls cost whatever the person's plan charges, and a number outside their country may cost more. Toll free numbers work the same as any other.

Write the number so it dials from anywhere

Use the international form: a +, the country code, then the number without its leading zero. A UK number written 020 7946 0000 becomes +44 20 7946 0000. A number without a + only dials correctly from inside its own country, so a code printed for local customers will fail for a visitor from abroad.

The tool cleans what you type and shows you the result:

• +1 (555) 010-0199 becomes +15550100199
• 555.010.0199 becomes 5550100199, with a note that there is no country code
• (020) 7946 0000 becomes 02079460000, also with that note
• +44 (0)20 7946 0000 becomes +442079460000, with a note that the (0) was dropped
• *123# is kept, and the link holds *123%23, because a # written as it is would be cut off as the end of the link

The (0) in brackets is the zero people dial inside the country and leave out from abroad, so the tool drops it, but only when it comes straight after the country code. A 0 that is not in brackets stays, because in some countries, Italy among them, it is part of the number: +39 06 1234 5678 is kept as it is.

A + sign is only accepted as the first character. A number such as ++1 555 010 0199 or 1+555 010 0199 is refused with a message, because the tool would have to guess what you meant. A number with fewer than three digits is refused, and one with more than 15 is flagged, because real phone numbers are between those lengths. A dial code with a or a # needs at least two digits. Phones handle links with or # in them in different ways, and some will not dial them at all, so scan the finished code on the phones people will use.

What it cannot do

Extensions: phones do not agree on how to dial an extension from a link, so a number written with ext 123 has the extension dropped, with a note. Put the extension in words next to the code, or use a direct number.

Letters: a vanity number such as 1-800-FLOWERS cannot be dialled as it stands. Type the digits that the letters stand for.

Several numbers: one code holds one number. To share a name, a mobile and a work number together, use a contact QR code.

Call, text or save: which kind of code

Pick the kind of code by what you want the person to do next:

• Call now: this page. Good for a shop front, a van, a repair sticker or a "call the owner" tag.
• Send a message: an SMS QR code opens a text with your message already written.
• Keep your details: a contact QR code saves the number, name and email.

A phone code is among the easiest to scan. At 21 by 21 squares, a code printed 2 cm wide has squares of about 0.7 mm. Anyone can read the number from the code, so do not put a private number on a tag or poster that strangers will see.