| Nucleus | Spin | Abundance | Receptivity (1H) | 400 Mercury (MHz) | 400 SGM (MHz) | 500 Varian (MHz) | 600 Varian (MHz) | Shift Range (ppm) |
| 39K | 3/2 | 93.2581% | 0.000476 | —.— | 18.673 | 23.323 | 27.999 | -30 -> 40 |
| 40K | 4 | 0.0117% | 0.000000612 | —.— | 23.245 | 29.035 | 34.854 | -30 -> 40 |
| 41K | 3/2 | 6.7302% | 0.00000568 | —.— | 10.247 | 12.800 | 15.369 | -30 -> 40 |