Data Cleaning & Spreadsheets

How to Standardize International Phone Numbers to E.164 Format in Excel & CSV

Marcus Vance
Marcus Vance
Principal RevOps & Data Architect
October 10, 2026 7 min read
TL;DR / Quick Summary

E.164 format represents phone numbers with a leading plus sign, country code, and subscriber number without hyphens or spaces (e.g. +14155552671). Standardize them automatically in Olonyn.

Why CRMs and Dialers Require E.164 Formatting

Telephony APIs like Twilio and cloud dialers in HubSpot will fail to route SMS or calls if numbers contain parentheses, spaces, or missing country prefixes.

Frequently Asked Questions

What if my CSV doesn't specify the prospect's country code?
Olonyn uses the prospect's city or state column to infer the correct international calling code automatically.
Marcus Vance
Written by Marcus Vance
Principal RevOps & Data Architect
Former data consultant who automated enterprise ETL pipelines, CSV data normalization, and B2B pipeline intelligence models.
Olonyn

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