FilePrepLab — KDP Size Companion

Offline paperback spine and cover-size estimates. Open a manual companion on KDP; confirm final files with Amazon’s official tools.

FilePrepLab — KDP Size Companion Estimate paperback spine width and full cover dimensions from your own book settings. Enter the manuscript page count, trim size, and ink/paper combination in a compact popup. The calculator works offline. Choose 5 × 8, 6 × 9, or 8.5 × 11 inches, with black ink on white or cream paper, standard color on white paper, or premium color on white paper. Odd manuscript counts round up to an even production count. Results show inches, millimeters, a rounded 300 DPI canvas size, and outer cover bleed. Invalid inputs clear the previous result and explain the supported boundary. On https://kdp.amazon.com, click “Open KDP sidebar” to display a manual companion. It appears only after your click. The extension does not inspect manuscripts or uploaded files, read Amazon form fields, identify real rejection errors, fill forms, or submit changes. Remember your three manual settings only if you choose to save them on this device. Turn remembering off or use Reset to remove saved settings. The extension uses the current-tab URL temporarily to limit the sidebar to KDP; it does not save or transmit that URL. There is no cloud sync, telemetry, account requirement, or background network fetch. Open FilePrepLab's web calculator and PNG reference-export entry. The PNG exporter runs on the website, requires the internet, and asks you to review your settings there. It does not export inside the extension, create an editable Canva template, or produce finished artwork. A separate link provides free PSD working files for exactly 150 production pages. Destination websites follow their own privacy policies. This independent sizing aid is not affiliated with Amazon. It supports only the listed paperback presets; hardcover, custom trim and groundwood paper are outside this release. Dimensions and reference guides cannot guarantee acceptance. Check your exact book settings with KDP's official Cover Calculator, inspect the final cover PDF, and use Print Previewer before submission.