Practical guide · dimensions explained
A4 vs US Letter in pixels: rounding and layout differences
Why A4 has no single pixel size, when 2481 beats 2480 at 300 PPI, and what changes when an A4 layout moves to US Letter.
Reviewed September 28, 2026 · Worked examples calculated for this guide
Illustration of the related tool’s example; proportions only.
Paper has a physical size, not one pixel size
A4 is 210 × 297 millimeters. US Letter is 8.5 × 11 inches, exactly 215.9 × 279.4 millimeters. Letter is wider and shorter. Neither format has a single pixel size: choose the image density first. Rotating the sheet swaps width and height; it does not turn one paper format into the other.
A4 examples, rounded to the nearest pixel
Convert each millimeter dimension to inches by dividing by 25.4, multiply by PPI, then round each side. A4 at 150 PPI is 1240 × 1754 pixels; at 300 PPI it is 2480 × 3508 pixels; at 600 PPI it is 4961 × 7016 pixels. These are computed canvas examples, not alternative definitions of A4.
When 2481 is the right width
At 300 PPI, A4’s exact width is approximately 2480.315 pixels. Rounding to 2480 produces a width density just below 300 PPI. Rounding up to 2481 avoids that shortfall. Our reference table lets you choose between nearest and upward rounding, and the canvas calculator shows the effective density of each rounded axis.
Moving between A4 and Letter
At 300 PPI, Letter is exactly 2550 × 3300 pixels. Copying an A4 layout into Letter with uniform scaling can produce extra space or crop part of the page because their proportions differ. Use the document scaling calculator with the intended margins. The paper reference gives nominal sheet sizes, not your printer’s printable area, tray support or borderless capability.
Reference notes
References checked September 28, 2026. Calculations and worked examples are our own.