How to import large CSV files

Excel

1. Open a blank workbook.
2. Go to Data → From Text/CSV and choose the file.
3. Set File origin to 65001: Unicode (UTF-8).
4. Click Transform Data, select the phone and postcode columns and set their type to Text. This keeps leading zeros and "+" prefixes.
5. Click Close & Load.

Excel handles about one million rows per sheet. For bigger merges, load into Power Query's data model or a database.

Google Sheets

Google Sheets has a limit of 10 million cells per spreadsheet. A 50,000-row file with 12 columns is 600,000 cells — fine. Twenty packs merged into one sheet would exceed it; keep packs in separate spreadsheets or use a database.

Databases (PostgreSQL example)

CREATE TABLE contacts (company text, phone text, email text, website text, city text, postcode text);
\copy contacts FROM 'UK-0007.csv' WITH (FORMAT csv, HEADER true, ENCODING 'UTF8');

Store phone numbers and postcodes as text, never as numbers.

CRMs

Most CRMs cap a single import (often 10k–100k rows). Split the file first — our free CSV splitter does this in your browser — and import the parts one at a time, mapping columns explicitly.