Bulk ISBN Converter
The bulk ISBN converter is the fastest way to convert a list of ISBNs. Paste your codes in any format (comma-separated, space-separated, tab-separated, or one per line) and click Convert. Non-ISBN text is passed through unchanged, so you can paste a raw catalogue export without preprocessing.
Conversion options
Three conversion directions are available, each independently selectable:
- ISBN-10 to ISBN-13: Prepends "978" to the ISBN-10 and recalculates the check digit using the modulo-11 algorithm. Every valid ISBN-10 has a corresponding ISBN-13.
- ISBN-13 to ISBN-10: Removes the "978" prefix and recalculates the 10-digit check digit. Only possible for "978"-prefixed ISBN-13s. ISBN-13 codes with a "979" prefix are outside the addressable range of ISBN-10 and are left unchanged.
- UPC-A to EAN-13: Prepends a leading zero to the 12-digit UPC to produce a 13-digit EAN. Standard transformation for products sold in both North American and international markets.
Supported input
Enter ISBNs separated by spaces, tabs, or commas. Quoted ISBNs (e.g. "0525536221") are handled correctly. Mixed content is fine: only valid ISBN-10, ISBN-13, EAN-13, and UPC-A codes are converted; everything else passes through as-is.
Example
9780735211292, non-isbn text is ignored, 0735211292
After conversion, the updated ISBNs replace the originals in the same text area.
The 979-prefix limitation
EANs and ISBN-13s beginning with "979" cannot be converted to ISBN-10. The ISBN-10 format was allocated specifically for the "978" EAN namespace; the "979" prefix was introduced by the International ISBN Agency to expand ISBN capacity beyond what that range could accommodate. No valid 10-digit representation exists for these codes. ISBNConverter.com leaves them unchanged rather than producing an invalid result. When converting ISBN-13 to ISBN-10, enable the option and these codes will simply pass through.
File Upload Converter
The file upload converter takes a structured or plain text file, converts all recognised ISBNs within it, and returns a converted copy as a download. Your original file is never stored or modified. Uploaded files are deleted immediately after processing.
Supported file types
- Microsoft Excel (.xlsx)
- Comma-separated (.csv)
- Tab-separated (.tsv, .tab)
- Plain text (.txt)
- Markdown (.md)
Column placement options
For structured files (Excel, CSV, TSV), you can control where converted ISBNs appear in the output:
- After ISBN column: The converted value is inserted immediately to the right of the detected ISBN column.
- Before ISBN column: The converted value is inserted immediately to the left.
- End of row: The converted value is appended as the last column in each row.
- Start of row: The converted value is prepended as the first column in each row.
- In place (replace original): The converted value replaces the original ISBN. The column structure is unchanged.
For plain text and Markdown files, only In place is available: the converter replaces each detected ISBN where it appears in the file.
Conversion options
The same three conversion directions apply as in the bulk converter: ISBN-10 → ISBN-13, ISBN-13 → ISBN-10, and UPC → EAN. Each can be enabled or disabled independently before uploading.
REST API
The ISBN Converter API converts any single ISBN code via a GET request authenticated with an X-API-Key header. The full conversion endpoint returns all applicable formats (isbn10, isbn13, ean, upc) for the input code. A targeted endpoint returns only the requested format.
API keys are created and managed from the API page after signing in. Each successful conversion consumes one credit.
Troubleshooting
If a valid-looking ISBN is not being recognised, check for: extra spaces or invisible characters surrounding the code; dashes or hyphens within the ISBN (we handle these automatically, but verify the digit count if the code is still rejected, e.g. 978-0-262-03384-8); quote characters around the code (the bulk converter handles "0525536221" correctly); and incorrect digit counts caused by leading zeros being stripped when opening a CSV in Microsoft Excel.
If a code passes an external ISBN validator but is still rejected here, contact us with the specific code and we will investigate.