A4 versus Letter: which dimension limits the fit?
A4 is 210 × 297 mm; Letter is 215.9 × 279.4 mm. The extra width of Letter does not compensate for its shorter height. With no reserved margin, the height ratio limits the fit to 94.07%. With 5 mm on each edge, the usable Letter area is 205.9 × 269.4 mm and the limit is 90.71%.
Paper dimensions at a glance
| Paper | Width × height (mm) | Width × height (inches, rounded) |
|---|---|---|
| A3 | 297 × 420 | 11.69 × 16.54 |
| A4 | 210 × 297 | 8.27 × 11.69 |
| A5 | 148 × 210 | 5.83 × 8.27 |
| Letter | 215.9 × 279.4 | 8.5 × 11 |
| Half Letter | 139.7 × 215.9 | 5.5 × 8.5 |
How to read the overlay
The rectangles share a top-left corner so differences in width and height remain visible. Screen size is not physical paper size. Rotating the source changes the calculation, but the target stays portrait. The tool preserves proportions and assumes equal margins on all four target edges.
A zero margin is a geometric comparison, not a borderless-printing setting. For actual printing, use the margin supported by your selected printer mode. If physical dimensions must remain unchanged, resizing may not be appropriate.
A4-to-Letter worked example · A5 versus Half Letter planner fit · Understanding printer margins