| Displacement | 1142t standard, 1383t surface, 1768t submerged |
|---|---|
| Length | 82.0m wl, 85.2m oa |
| Width | 7.5m |
| Draught | 4.42m |
| Machinery | 2-shaft diesel and electric motor, 2400bhp surfaceC1100shp submerged |
| Speed | 14.5kt surfaceC7kt submerged |
| Armament | 4-53cm TT, 1-14cm/40cal gun, 42 mines |
| Complement | 51 - 70 |
| Name | Plan | Builder | Laid down | Launch | Complete | ||
|---|---|---|---|---|---|---|---|
| I-21 (SS-48) (I-121) | FY1923 | Kawasaki, Kobe | 1924.10.20 | 1926. 3.30 | 1927. 3.31 | SS1 | 1938. 6. 1 renamed (I-121) 1945.11.30 disc 1946. 4.30 scuttled |
| I-22 (SS-49) (I-122) | FY1923 | Kawasaki, Kobe | 1925. 2.28 | 1926.11. 8 | 1927.10.28 | SS1 | 1938. 6. 1 renamed (I-122) 1945. 6.10 sunk (torpedoed, Sea of Japan) [37.29N, 137.25E] 1945. 9.15 disc |
| I-23 (SS-50) (I-123) | FY1923 | Kawasaki, Kobe | 1925. 6.12 | 1927. 3.19 | 1928. 4.28 | SS1 | 1938. 6. 1 renamed (I-123) 1942. 8.29 sunk (action, off Guadalcanal) [09.21S, 160.43E] 1942. 9. 1 missing 1942.10. 5 disc |
| I-24 (I-124) | FY1923 | Kawasaki, Kobe | 1926. 4.17 | 1927.12.12 | 1928.12.10 | SS1 | 1938. 6. 1 renamed (I-124) 1942. 1.20 sunk (action, off Port Darwin) [12.05S, 130.06E] 1942. 1.20 missing 1942. 4.30 disc |