Why does my printer say the wrong paper size is loaded?
A paper-size mismatch usually means the print job's requested size does not agree with the paper size configured for the selected tray. Depending on the printer, that configuration may come from tray guide positions, control-panel settings, driver settings, or automatic media detection. A familiar label can hide different dimensions. ISO B5 is 176 × 250 mm, while JIS B5 is 182 × 257 mm. Likewise, A6 and 4 × 6 photo paper are different sheets. Verify the exact dimensions in both driver and tray configuration instead of choosing the nearest-looking name.
The three settings that must agree
- Document page size: the dimensions saved in the file or application.
- Printer driver paper size: the destination sheet requested by the print job.
- Sheet physically loaded: the actual paper in the selected tray, including its registered size on the printer.
For a paper-size or mismatch warning, one of these three usually disagrees; check them before assuming a fault. For cropped or incomplete output, check printable margins, the application's print area and scaling too. If you intentionally print onto a different size, select that destination and scale the source document to fit.
Fix it on Windows
Measure the sheet and check its full designation
Check the package or measure both edges in millimetres. Open File > Print > Printer Properties and inspect the dimensions behind the selected name; B5 may mean the Japanese rather than ISO format.
Match the Windows driver to the loaded sheet
In Windows 11, open Start > Settings > Bluetooth & devices > Printers & scanners > your printer > Printing preferences. In Windows 10, use Settings > Devices > Printers & scanners > your printer > Manage > Printing preferences. Select the loaded Paper Size and Paper Source. Drivers may place these under Paper/Quality, Layout or Advanced.
Define a supported custom size
In Printing preferences, look for Paper Size > Custom or User Defined; the exact path is driver-specific. Enter the measured width and height only if they meet the printer’s supported size range, save it, and select it in the application too.
Send one fresh test page
Cancel the old job in the print queue and send one page again after changing the settings. A queued job can retain the earlier size. Check the preview and printed margins before printing the remaining copies.
Fix it on macOS
Match the macOS print job to the loaded sheet
Open File > Print, select the intended printer and choose Paper Size. Expand Show Details if your version displays that button. Under Paper Feed or the manufacturer’s printer options, select the tray holding that sheet. These controls vary by application, driver and AirPrint support.
Check or create the precise paper dimensions
Where supported, open File > Print > Paper Size > Manage Custom Sizes, click Add (+), and enter the width, height and non-printable margins. Some applications expose this through File > Page Setup instead.
Check support before using the custom preset
Select the saved custom size in File > Print and choose a supported tray. Creating a custom size does not extend the printer’s physical feed limits; if AirPrint does not offer it, check the manufacturer’s supported driver options.
Send one fresh test page
Cancel the old job in the print queue and send one page again after changing the settings. A queued job can retain the earlier size. Check the preview and printed margins before printing the remaining copies.
If it still will not print
- Rest the tray guides against the stack without bowing the sheets. Use one size and type per stack.
- Check the selected tray. An automatic source can choose a different stack from the one you checked.
- For custom paper, confirm that the size is defined in the driver and supported by the chosen tray. A custom preset cannot make a narrow paper path wider.
- If the settings agree and a simple test still fails, check the manufacturer's support page for your exact model's driver and firmware updates. Follow its update instructions and keep power connected throughout.
Some models allow a mismatch override or Continue option. That may let the job print, but the margins can sit unevenly on the sheet or content can be cut off. Use it only after checking what will be printed; it is not a replacement for matching the settings.