Excel Keeps Dropping Leading Zeros in ZIP Codes

Why This Happens

When you enter ZIP codes, product IDs, or other number codes in Excel, it treats them as regular numbers. Since numbers don’t start with zeros, Excel automatically removes them. If your ZIP code is "01234", Excel will turn it into "1234"—which isn't correct.

This also affects long numbers like credit card details, as Excel only supports 15 digits of precision and replaces anything beyond that with zeros.

How to Keep Leading Zeros

Method 1: Use a Custom Number Format

If you only need to fix the issue inside Excel (without exporting the data), follow these steps:

1. Select the cells with ZIP codes or number codes.
2. Go to the Home tab and click the small Number Format launcher (bottom-right of the "Number" group).
3. In the Category list, select Custom.
4. In the Type box, enter 00000 (for five-digit ZIP codes).
5. Click OK—this forces Excel to display the leading zeros.