Free tool
Phone number formatter: paste a list, get E.164, deduplicated
The same normaliser DialSheet's importer uses, in a page. Paste numbers in any format, including the “4155552671.0” and “4.15556E+09” forms a spreadsheet leaves behind, and get +14155552671 back with duplicates removed and extensions stripped. Rows that cannot be parsed are listed, not silently dropped. Nothing leaves your browser.
E.164, deduplicated
Why lists arrive broken
A vendor exports numbers in whatever format their database kept them; then the file passes through Excel or Google Sheets, which reads the column as a number, drops the plus, and past about eleven digits writes the value out in scientific notation. Twilio and every dialer built on it want E.164, and reject the rest with error 21217 or 13224. The recoverable damage is undone here; the unrecoverable rows are the ones with digits missing, and the fix for those is the source file with the column formatted as text. The full method, including the Google Sheets formula and the trunk-zero rules for non-US lists, is in how to clean a lead list before you dial it.
Questions people actually ask
What is E.164 format?
The international standard a carrier API expects: a plus sign, the country code, and the national number with no spaces, brackets, dots or dashes, at most fifteen digits. A San Francisco number is +14155552671; a London mobile is +447700900123. Twilio rejects anything else with error 21217 or 13224, and most dialers and CRMs store numbers this way so they match across systems.
Is my list uploaded anywhere?
No. The page runs the formatting in your browser with Google's libphonenumber rules; nothing you paste is sent to a server, and closing the tab discards it. Copy or download the result when you are done.
Why do some numbers show as "could not parse"?
Because they are not dialable as written: seven digits with no area code, a number with letters in it, two numbers in one cell, or a value Excel rounded into 4.15556E+09 where the real digits were lost. The tool undoes the recoverable spreadsheet damage (a trailing ".0", and scientific notation where the digits survive) and lists the rest so you can fix the source rather than dial a wrong number.
What happens to extensions?
They are stripped before formatting, because a carrier dials the number and the extension is entered after the call connects. Keep extensions in their own column in your list so the dialer can send the digits after connect.
Can I use this for UK or Australian lists?
Numbers already carrying a country code (+44…, +61…) format correctly. Numbers without one are interpreted in the default country you pick, currently US or Canada; a bare UK number such as 07700 900123 will not parse as US. Add +44 in the sheet first, or use the Google Sheets formula in our list-cleaning guide, which covers trunk-zero rules for the UK, Ireland and Australia.
Or skip the tool and import the vendor's file as it is.
DialSheet's importer runs this normaliser on every row, maps the columns, dedupes on the clean number, and reports what it could not parse. Free for one person up to 500 leads, $29 per 3 seats after.
Import a list