Paper sizes
Decided: a P series, made the same way as the A series: each size halves the one before, sides in the ratio 1 : √2, and P0 = 1 square pace (as A0 = 1 m²).
Why: halving keeps the shape, which is why the A series works; only the starting size needs changing. P5 lands almost exactly between A4 and US Letter (its width is Letter's 8.5 in), so one sheet can replace both.
Advantage: one sheet replaces both A4 and Letter, and every size keeps the same shape.
| Size | mm (dec) | Close to |
|---|---|---|
| P0 | 1,221 × 1,727 | A0 (841 × 1,189), 2.11 m² |
| P3 | 432 × 611 | A2 (420 × 594) |
| P4 | 305 × 432 | A3 (297 × 420) |
| P5 | 215.9 × 305 | A4 (210 × 297), Letter (215.9 × 279) |
| P6 | 153 × 216 | A5 (148 × 210) |
| P7 | 108 × 153 | A6 postcard (105 × 148) |
- Sides aren't round in uncs (P5 = 1;95 × 2;63 un), for the same reason A4 isn't round in mm: √2