PaperSize provides the reviewed A4 dimensions. DpiCalc applies arbitrary density arithmetic. With the contract “at least 300 source pixels per inch,” each fractional pixel requirement rounds upward independently rather than to the nearest familiar table value.
Convert 210 mm exactly
Because one inch is exactly 25.4 mm, 210 mm equals 2100/254 = 1050/127 inches. Multiplying by 300 gives 315000/127 = 2480.314960… pixels. The smallest whole count that does not undershoot 300 PPI is therefore 2481 pixels.
Convert 297 mm independently
297 mm equals 1485/127 inches. At 300 PPI the exact requirement is 445500/127 = 3507.874015… pixels, so the whole-pixel ceiling is 3508. Width and height are not inferred from a rounded ratio; each comes from its own exact physical dimension.
Nearest-pixel tables may differ by one
Many A4 references quote 2480 × 3508 pixels at 300 PPI because they round to the nearest pixel. That is a valid reporting convention, but 2480 pixels across exactly 210 mm is slightly below 300 PPI. DpiCalc’s print-to-pixels mode uses an explicit minimum-density ceiling, so it reports 2481 × 3508.
Add production requirements separately
A final A4 job may require bleed beyond 210 × 297 mm, a crop, a specific profile, or a provider template. Apply those dimensions before calculating required pixels. The example proves only the arithmetic for the exact trimmed rectangle at the stated source density.