KDP Trim Size Guide
Quick answer
Trim size is the finished physical size of the paperback after cutting. KDP validates the selected trim size against the actual PDF dimensions. A 6x9 book must export as 6 x 9 inches for no bleed, or with the correct bleed allowance when bleed is enabled. The same rule applies to 8.5x11, A5, and other supported KDP sizes: the dashboard selection and PDF size must match.
When this matters
Trim size matters when you choose a paperback size, export from Word or InDesign, resize a PDF, or switch from KDP to another platform. It is a common cause of interior size mismatch, trim size mismatch, and incorrect PDF export size errors.
Common causes
- The selected KDP trim size does not match the PDF page size.
- A 6x9 or 8.5x11 source document was exported through a printer preset.
- A5 or metric sizing was converted incorrectly.
- Bleed was enabled but the PDF was exported at no-bleed size.
- Export scaling changed the MediaBox dimensions.
- Interior and cover were built from different trim assumptions.
How to check
Open the final PDF properties and confirm width and height in inches. Compare that against the KDP selected trim size and bleed setting. Check a sample of pages across the document to make sure section breaks or merged PDFs did not create mixed page sizes.
Tool
Use the Trim Size Calculator to compare selected trim size, bleed mode, and final PDF dimensions.
Related KDP errors
Before uploading again
Use the pre-upload checklist and run the risk scan after validating the exact PDF dimensions.