A4 vs Letter：A3・A6用紙サイズガイド

If you've ever printed a template and the lines looked “slightly off”, you might have mixed A4 and US Letter. They’re close in size, but not interchangeable.

The key dimensions

Because Letter is a bit wider and shorter, printing an A4 PDF on Letter often triggers scaling.

Choose A4 when

• You’re in regions where A4 is the default paper stock
• You need consistent scaling between sizes (A3 → A4 → A5) under ISO 216
• You share templates internationally

Choose Letter (letter paper) when

• Your printer tray and supplies are set up for Letter or letter paper
• Your school/workplace expects Letter/Legal formats
• Your binders and folders are Letter-sized

Avoid “mystery scaling” in PDFs

To keep line spacing and grid sizes accurate:

• Match the paper size in the print dialog to the document
• Print at Actual Size / 100%
• Avoid Fit to Page or Shrink to Printable Area

Practical tip: keep separate template sets

If you publish templates, it’s usually better to provide two versions:

• One optimized for A4
• One optimized for Letter

That removes the temptation for the printer to auto-fit.

If you’re using PaperGens, start with a US-friendly template like:

• College ruled template

or a grid template:

• Graph paper 1/4 inch

Summary

• A4 is slightly narrower and taller than Letter (letter paper).
• Mixing them often leads to scaling.
• The safest workflow is matching paper size + printing at 100%.