JAPANESE WHET STONE
SIZE AND GRADING SCALE
The Japanese grading scale is based on size and is recognized and used in the manufacturing and marketing of traditional natural whetstones. Larger stones of a given quality and purity are and always have been more difficult to obtain in the natural state, and therefore command a higher market value based on rarity.
| name | minimum size in mm. | base market price in yen |
| #24 long/uncut stone | any size bigger than below | |
| #24 | 218 x 78 x 24+ | 37,500 yen |
| #30 | 205 x 75 x 24+ | 30,000 |
| #40 | 205 x 75 x 24- | 22,500 |
| #60 | 195 x 70 x 20+ | 12,000 |
| #80 | 180 x 63 x 15+ | 6,750 |
| #100 | 160 x 58 x 15+ | 4,500 |
| smaller sizes | odd shapes | |
| konbu | 128 x 158 | 10,000 |
| razor | 136 x 82 | 4,000 |
| cross piece | 180 x 60 | 3,000 |
| sickle | 120 x 36 | 2,000 |
| chips/kappa | smaller | 0-? |