A6 is exactly 105 × 148 mm. At 300 image pixels per inch, divide each side by the exact 25.4 mm-per-inch conversion and multiply by 300. The decimal results are approximately 1240.1575 × 1748.0315, displayed as 1240 × 1748 nearest whole pixels. Orientation changes only their order.
Calculate the 105 mm side
Pixel width = 105 ÷ 25.4 × 300 = 1240.1575… pixels. Nearest-whole-pixel rounding gives 1240. PaperSize retains the exact millimetre input and decimal calculation rather than first rounding A6 to an approximate inch size.
Calculate the 148 mm side
Pixel height = 148 ÷ 25.4 × 300 = 1748.0315… pixels, displayed as 1748. The portrait canvas is 1240 × 1748 and landscape is 1748 × 1240. Both orientations are one A6 entity and do not justify separate indexed result pages.
Keep printer requirements outside the base canvas
The 1240 × 1748 result represents exact A6 at 300 PPI after nearest-pixel rounding. It does not include postal margins, bleed, safe zones, crop allowance, borders, or export requirements. Follow the printer or postal specification instead of treating this arithmetic as a complete production template.