The Divine Proportion, or Golden Ratio, is equal to (sqrt(5)+1)/2, approximately 1.61803. It appears frequently in nature, the ancient Egyptians probably knew about it, the ancient Greeks certainly knew about it, and the artists and architects of renaissance Europe were obsessed with it.
Moleskine "pocket" notebooks are 9x14cm in size, only 4% from the Golden Ratio (the long side is approximately 5mm short). A size of 8x13cm would be even closer (within 0.5%) but would have 17% less area per page. 8.9x14.4cm would be closer still (within 0.004%) but would not have the convenience of whole-centimetre dimensions. 9x14cm therefore represents a balance between useful area, pocketable size and convenient dimensions while remaining very close in aspect ratio to the long-held ideal. The "large" notebooks, at 13x21cm, are within 0.2%.
This table shows the approximate proportions between the Golden Ratio and the possibilities mentioned, with the aspect ratios of ISO standard paper (A0, A1 etc) and a square included for reference.
| 13/8 | 1.00431 | |
| 144/89 | 0.99997 | |
| 21/13 | 0.99836 | Moleskine large |
| 14/9 | 0.96139 | Moleskine pocket |
| sqrt(2) | 0.87403 | ISO paper |
| 1 | 0.61803 | Square |
The last line, incidentally, shows another property of the Golden Ratio: its reciprocal is equal to the ratio-1. There are plenty of Golden Ratio resources on the web for those who wish to know more.
2005-02-28